In Plato's Apology, Socrates' student Plato recorded Socrates' trial on accusations of corrupting the youth. In this dialogue Socrates mentions that he does not receive any direct payment for his teachings. In universities it is often taught that Socrates was given "gifts or donations" from his wealthier followers. Many philosophers acted as polical figures and tutors (e.g. Cicero who was part of the Roman senate and Aristotle who tutored Alexander the Great), which acted as their means of sustenance. Figures like Seneca, the famous stoic, in fact wrote after retirement as advisor of emperor Nero.

In the Renaissance, especially in Italy, the courts and powerful families often patronized philosophers of sorts. For example the Medici's are know for their circle of Neoplatonists.

Primary Sources: Plato's Apology, Plutarch's Life of Alexander, Cicero's Letters, Seneca's Epistles.

Secondary sources: Kenneth R. Bartlett's A Short History of the Civilization of the Italian Renaissance.

Edit: First post and mobile format so sourcing is simple.