I don't make tons of money, but I usually get paid $15 - $20 an hour. For me, that's worked out to an actual income and pays the rent. I've made as much as $50 an hour, but those gigs are inconsistent and harder to get.
Artists will offer you gigs, and you can take them or not as you choose. If you want to plan your schedule around another job or your personal life, art modeling is a great job for you.
Artists appreciate good models. I've worked other jobs (retail and office work) with indifferent, ineffectual, and critical management and unfriendly, argumentative customers. I like how friendly and appreciative artists are, and how they genuinely enjoy the process of drawing - and communicate that to their models!
As a model, you help artists become better at creating beauty. I think that's pretty damn awesome.
As a model, I've met many talented professional artists. I enjoy meeting interesting people who live their passion, and it also means that if I want to buy art, I can usually see it (and possibly purchase it) before it gets to galleries and the general public.
When I'm modeling, I get time to think. And I don't have to constantly be interacting with the artists, so modeling feels a lot more like 'me' time than 'being social on the clock' time.
Nobody goes into art just to make money. Nobody's parents told them when they were young, "You know, you should really get a stable job with benefits and a high income like an illustrator!" Artists always want to be there. I enjoy working with people who are enjoying what they're doing, rather than just 'punching the clock'.
These days people have a lot of weird body image issues. While supermodels and other modeling gigs require 'perfect' bodies, art models are expected to be human. Sometimes anatomy is the focus, and an artist wants a muscular, defined model. Sometimes an artist wants to study different extremes of body types, or be imitating Rubens' work, and they want a fatter, voluptuous model. Most art models are normal people with normal body types - not really fat or muscular.