That sounds like a catastrophic idea. You're seriously considering going through 135 training, having a few jeopardy events, another employer reporting to your PRIA, because you can't afford $500 to rent a 152 for a 5 hours?
I think this is an extreme case of "penny wise, pound foolish".
Let's say Grant calls you and gives you a job in Alaska. You wash out of training. Suddenly you can only work for places like Mesa because of your fresh training failure. Only to save $500.
If you don't have $500. Open a new credit card, pay it off with the signing bonus from your regional.