It would also help if we knew the type of job you currently have and your skills so we could possibly offer some options. If you're looking to pocket ~$800 cash then you're talking long term on a minimum wage job or short term on a higher paying gig.

If you know anything about computers you could fairly easily earn $800 within a month doing your own thing fixing computers for people. Even installing Vista and cleaning up computers for people can earn some serious cash fast. I've done that just to help out people at work or friends of the family and earned hundreds in a couple days, depending on the problems I was fixing.