According to [0] Rome had more than 1 million inhabitants somewhere during the timespan of 100 AD to 200AD, which was a large portion of Italy's population. This is a huge amount of people. I guess that most of these people were slaves. Some were rich aristocrats and some were free Roman citizens that were poor.
I guess that most of jobs that are performed today by the so-called "working poor" were done by slaved in ancient Rome. The aristocrats have probably comparable occupations as today. I'm interested in knowing what a free but poor Roman citizen did.
I guess that their wages were higher than those of slaves and therefore nobody would hire them for the "working poor"-jobs. However, they also did not have the money to buy some slaves and start their own business and thus rise into what we would today call the middle class.
Further, most pre-industrialization societies needed to invest most of their labor force into agriculture to get themselves fed. That 1 million people in Rome certainly did not do agriculture and was a significant part of the Empire's population. Were there enough "productive" city jobs back then to employ 1 million people?
[0] https://en.wikipedia.org/wiki/Demography_of_the_Roman_Empire#Urbanization
I've answered this question incidentally many times, it's sort of my subfield. Here's one. The majority of the urban population was free, not servile, but the vast majority of the free population lived a life of abject poverty. Only a relatively few people in the cities could be said to have "occupations." The senatorial class was legally barred from engaging in business (although many did so anyway, through friends, dependents, or slaves) and made their money through land. The small group of equites generally were involved in mercantile activities or, particularly in the late Republic, we're contracted as publicans. But relatively few of the urban poor, or the urban population in general (the rural plebs are a different story) had any kind of steady employment at all. Apart from a relatively small subset of the plebs urbana (sometimes called the plebs media) who were themselves or were employed by shopkeepers, craftsmen, and other skilled workers, the vast majority of people in the city found work as day-laborers. The thread I linked to (and others like it, which I can probably hunt down if necessary) should explain better--I'm unfortunately on mobile, which prevents me from easily restating everything that I have on the subject (like I said, this is literally my subfield, so I could go on for a while if I had the ability)