I cannot say about western philosophers, so instead I will say about Chinese and Muslim philosophers instead. The Chinese philosophers that flourished during Spring and Autumn period acted like modern day consultants, they traveled from one state to another, offering services to the rulers. The services could be anything from teaching the sons of the rulers ethic, to codifying the law, to improving fortifications. It was how Confucius lived, as was his contemporaries and rivals such as Mozi.

In late Imperial China, after China was unified, usually philosophers were those who had passed Imperial Examination and employed by the empire as scholar-bureaucrats. Many neo-Confucianists thinkers were of this occupation.

In Muslims world during Muslims Golden Age, many philosophers are polymath, meaning they are not only excel in philosophy (which means expertise in both Greek philosophy and Islamic theology) but also expert in jurisprudence and sometimes medicine. These philosophers will be employed by rulers of Islamic caliphates or emirates as qadi (judge) to dispense justice among populations. For example the most celebrated Andalusian Muslim philosopher, Averroes, once was appointed as qadi in 1160, of Seville (modern-day Spain) and he served in many court appointments in Seville, Cordoba, and Morocco during his career.

I know Plato and Aristotle both had students that they taught.

Socrates was actually infamously poor, and it was this lifestyle that really mirrored, in a way, his entire philosophy. Socrates, as a young man, worked as a sculptor, as did his father. He was also, for some time, in the army and fought in the Peloponnesian war around 430 BC. He was considered a courageous soldier and was decorated after the battle of Potidaea.

As he continued his life and interest in philosophy, he lived very modestly compared to his contemporaries. He didn't have a formal classroom, and never wrote anything down, vowing to only use dialectic forms of communication to figure out philosophical ideas prominent at that time (what is courage, value, piety, etc.) Other philosophers and citizens from Athens described Socrates as extremely charismatic, something of a social addiction. He would go into the market and sit there all day, every day, engaging in long winded, complex and often heated philosophical discussions with who ever about topics that would come up. (Imagine a man so smart he could sit there and shake up your entire belief system right to its core, in front of dozens of people.)

He famously never bathed, didn't eat much, had a modest house and wife, was often barefoot, and basically lived off of donations people would give him while he would be walking around Athens or in the market having philosophical discussions with young men or members of the political hierarchy in Athens (which later got him into a lot of trouble, but that is another story).

Socrates was completely devoted to the life of philosophy. In the basic (Greek) understanding, philosophy, the word, actually means a love for wisdom. Socrates was considered the wisest man in all of Athens, and many defended that fact, except of course Socrates. He basically set out to figure out if he was indeed the wisest man in Athens and this led him to all sorts of crazy conversations with other philosophers and citizens in Athens. Its not that Socrates wandered the streets as a bum, he was certainly lower-middle class, but he always held the notion that modesty was an important principle that every so called "wise man" should keep close to his heart. He never took more than he needed, why? Because it would be unreasonable to Socrates.

“Contentment is natural wealth, luxury is artificial poverty.” - Socrates

P.S. I'm just a Philosophy major in university and one of my big interests is in Greek philosophy. I don't have citations for any of this but it's compiled from what I've read and heard in lectures.

Just a brief comment about whether Socrates was poor or not: though we don't know much about how Socrates made his living in his later life, it's mentioned in Plato's Apology (28e) - probably the closest representation in Plato's works of Socrates's actual thought - that Socrates fought with distinction as a hoplite. Hoplites in Athens had to provide for their own armor (p519):

The individual soldier had to provide his own equipment, apart from the shield and spear given him by the state... Thus in the classical system, only the citizens with means to arm themselves could be hoplites. There was a property-qualification for service.

Thus, at least early in his life, Socrates was well-to-do enough to meet the property qualification to become a hoplite - if he was poor, it was a condition of his later life.

I think I can help out though this only pertains to Western Philosophers.

Socrates was poor and lived an incredibly Spartan life. He was a solider before he was Plato's mouthpiece, and he was likely a tradesperson after that. As a Philosopher, who knows if he had a job or not. What is known is that he never took money for teaching (as was custom among the Sophists), but I imagine he was probably given food and drink as a guest though my memory is failing me as to if that ever happened in one of the dialogues.

This is relevant from the SEP:

After completing his two years of military training, Socrates was subject to being sent beyond the borders of Attica with the army, but these were years of relative peace, so he is likely to have practiced a trade, at least until he gave his mother in marriage to Chaeredemus. Only at the age of thirty was eligibility established for such responsibilities and offices as jury service, generalship, and Council (executive body for the sovereign Assembly), so Athenian men lived at home with their parents during those ten years, and—depending on their class in Athens' rigid four-class system, based on wealth and birth—they spent that period learning a trade or acquiring the skills in public speaking and persuasion that would serve them well in Athens' citizen Assembly and courts.

Plato was likely rich. In the introduction to the Republic (translated by Grube), it is said:

[Plato's] father, Ariston, was descended -or so legend has it- from Codrus, the last king of Athens; his mother, Perictione, was related to Solon, the first architect of the Athenian constitution. His family was aristocratic and well off.

Of course, it is important to note that he founded the Academy (at which Aristotle studied). I would imagine he taught there... though truth be told, I've no idea.

Aristotle was a teacher. He tutored Alexander the Great (at least briefly), and founded a school which was called the Lyceum. According to the SEP he likely also studied marine biology.

I guess to generalize, philosophers were often poor, wealthy, or professors.

Small digression: my favorite anecdote about one of the poorest of philosophers, Diogenese.

Thereupon many statesmen and philosophers came to Alexander with their congratulations, and he expected that Diogenes of Sinope also, who was tarrying in Corinth, would do likewise. But since that philosopher took not the slightest notice of Alexander, and continued to enjoy his leisure in the suburb Craneion, Alexander went in person to see him; and he found him lying in the sun. Diogenes raised himself up a little when he saw so many people coming towards him, and fixed his eyes upon Alexander. And when that monarch addressed him with greetings, and asked if he wanted anything, "Yes," said Diogenes, "stand a little out of my sun."[7] It is said that Alexander was so struck by this, and admired so much the haughtiness and grandeur of the man who had nothing but scorn for him, that he said to his followers, who were laughing and jesting about the philosopher as they went away, "But truly, if I were not Alexander, I would be Diogenes."

I study ancient Greek rhetoric, but admit (to my shame) that I do not possess the in-depth economical-logistical knowledge to answer your question in clear, direct terms. I suspect, though, that the question may have a couple of flawed assumptions about the past embedded within it, and I'd like to speak to those.

It's easy, even natural, to look back to Aristotle, Plato, and Socrates from the standpoint of a culture as deeply shaped by their intellectual accomplishments as ours is and assume that (a) they were incredibly popular and (b) being a philosopher was, as it is today, a particular and moderately well-demarcated sort of social role (a fact that comes in for special scorn from Schopenhauer, incidentally).

The former was simply not the case (see, e.g. Brunschwig and Lloyd 2000, 4-6). Socrates, of course, was a mixed bag--popular enough with some people to get himself killed by the greater number of people who didn't see him as all that great. Plato and Aristotle each had schools in Athens (and Aristotle was also, famously, tutor to Alexander the Great for a time--during which time Plato was succeeded as scholarch of the Academy by his nephew Speusippus, which is how Aristotle ended up founding his own school, the Lyceum, after his return from Macedonia), but they each also had plenty of competitors for the attention (and fees) of the Athenians. Indeed, as you can gather from my parenthetical comment above, Aristotle's Lyceum competed directly against the Academy that Plato founded (and that Aristotle studied in), among others.

For the latter point, it's worth bearing in mind that what we think of as "being a philosopher" was basically defined by Socrates. I'm happy to say more about that if it interests you, but I want to note here that Aristotle, Plato, and Socrates played three rather distinct roles in society.

I'm now going to address your question more directly. All of the following is drawn from a definitive reference work on ancient Greek philosophy: Greek Thought: A Guide to Classical Knowledge, edited by Jacques Brunschwig and Geoffrey Lloyd (and translated under the direction of Catherine Porter, 2000). Some relevant page numbers are given, in case you want to check this stuff out for yourself a bit further.

Socrates was an ascetic, but not impoverished. We don't know how exactly he was funded, but it seems likely that either (a) his wealthy friends kept him afloat or (b) he was born into an owning class. Stories about his financial circumstances are conflictual, since on the one hand we hear that his father was a sculptor and he trained to the same, while on the other hand we are told that he was a hoplite in the Peloponnesian War (and thus a member of one of the first three classes in the Athenian census--a position not in keeping with being the non-working son of a sculptor). Apart from his military duty, he was nearly as famous a homebody as, much, much later, Immanuel Kant. 746-747.

Plato came from money and, like most people who come from money and manage not to be too profligate, he kept it and got more of it. Though refusing his familial duties (marry, have citizen-sons) to devote his life to philosophy, he seems nonetheless to have carried his family's substantial resources with him as he set about founding his school, the Academy. 672-674.

Like Plato, Aristotle got a good start in life. A doctor's son at a time when medical knowledge was a family affair and physicians traced their lineages back to Asclepius, god of medicine, his family connections in the Macedonian court may have played a role in his eventual tutorship (beginning when Aristotle was 41) of Alexander (before the latter got Great, of course). Beyond his salary as Alexander's tutor and later on his fees from the Lyceum, information on Aristotle's specific means of sustenance--especially in earlier adulthood--is scarce, though we do know that he remained at the Academy in some capacity for a full 20 years after his arrival at 17. 554-557.

Like I said, ancient Greek economics is really not my field, but I did consult one other source I had here on the shelves: Chester Starr's The Economic and Social Growth of Early Greece: 800-500 B.C. (1977). This, unfortunately, does not go up to A/P/S's times, but it does offer some general insight into the economic motivations of the wealthy in the era immediately preceding Socrates:

A man who had chremata [lit. "useful things"] could consider himself plousios, that is, able to live without physical labor and to afford the luxuries of the day; the unfortunate man beset by penia, on the other hand, had to work for his living and could have no share in the good things.

The answers to your question hinge, I think, on whether Aristotle, Plato, and Socrates each were plousios by inheritance. If so, we can think of them as exceptionally productive trust-fund babies. This is almost certainly the case for Plato, was likely the case for Aristotle, and may or may not have been the case for Socrates.

I hope, if nothing else, all this offers some useful further context :-).

Socrates, by his own admission during his defense at trial, was actually very poor. Like all Athenians he served in the military when he was younger, and was even noted for bravery. There are surprisingly few sources on his young life, but some suggest he was a sculptor at some point. Unlike his student Plato, Socrates never actually ran a school, preferring instead to teach in public areas. Understand he didn't really teach lessons in the way we understand, he never held a class. He and his students would wander Athens having detailed discussions about morality and life. When they encountered an outsider, Socrates would likewise critique the beliefs of that person, leading him to be quite an unpopular figure in his city.

His student Plato, and in turn his student Aristotle, took a more traditional route, running schools and tutoring the sons of powerful Greeks. The Platonic Academy is one of the most noted schools in Ancient Greece, and Aristotle would find himself in the employ of Phillip of Macedonia tutoring his son Alexander.

Others have talked about Plato, Aristotle and Socrates, but I always thought Thales (The earliest known Greek philosopher) had an interesting approach. He bought up all the olive presses in a region, giving himself a monopoly and he used that to charge very high prices to set himself up. He probably could have given Adam Smith a few tips.

Socrates and Plato both made money teaching rhetoric to students, basically selling their philosophy and rhetorical skills to those that could pay, mostly young men who wanted to enter politics. This is apparent throught-out the Socratic dialogues (despite Socrates excoriating the Sophists for doing the same) and there's no reason to believe Plato didn't do the same. Aristotle, of course, made him money the same way, though he had a more famous and successful (?) pupil is Alexander.

There's been at least one thread on this in the past. There may be others.