How would getting a part-time job affect my financial aid for school?

I'm going to college entirely on my financial aid. My family can't afford it otherwise.

We're having a bit of trouble paying for gas and things like that right now, so I thought that getting a job might help out a bit. However, I'm afraid that it might affect my financial aid from FAFSA and TAP.

I've heard that there's a limit to how much extra money you can make before it affects your financial aid.... Any ideas on this?