Some things to consider...
You described the FBO you work for as being "too broke to have us work full time." I wouldn't put any stock in the promises your employer makes. If they are that broke, they could be gone at any time. I would DEFINITELY not put any money up front for training.
Second, the minimums at most regionals is at or near 1500 hours. My guess is they will be asking for ATPs before the deadline is reached. So, you might as well figure you will need an ATP or be darn close before you get on with the regionals.
You mentioned losing money and working hard to dig your way out. I would have all the money in the bank for a CFI BEFORE you start so you don't need to go into debt again. It sure is easier to live on first year FO pay when you don't need to carry a loan payment.
Good luck