If you're in SF (other major cities as well, I'm not exactly sure which ones) and have a car, look into becoming a
Lyft driver. I have a real job, but I am a lyft driver as well. Drivers get to keep 85% of the fare which is pretty good. I give a total of like 3-4 people a ride per day before and after going into my regular job, that's like $30-40/day right there which pays for my gas and toll + some. You can make a lot more if you drive the whole day, especially friday and saturday nights, but I don't do that. The extra money is just a plus to me, being a driver allows me to network and meet new people. I've met tons of people that work in the same industry/field as me and we trade business cards and what not. There's also a lot of cute women that use lyft. Every time a cutie gets in my car, I make it a challenge to get their number before the ride is over.
So far it's working out pretty well.