Is there any other way to gain more money, other than the shift at the fast good restaurant?
Finish the A Helping Hand storyline and choose to not settle the debt for Patrick andyou should come out with a large chunk of money.
You can also finish Sexcavation Expidition for some cash.
Finally, once you're in the sugar daddy storyline (A Taste of Sugar), you'll get a black credit card which can help you buy many items without using your money.