Well, isn't the pay enough to pay the student accomodation while working as FI?
Erm no... You get 'paid' only when flying. If you are sat on the bench doing nothing then you don't get anything.
You also get paid peanuts - you are there for Optional Practical Training - not employment.
You will also require to get yourself insurance etc. You don't want to be in an accident that might be of your making. Plus you would want health insurance etc.