I think the key is not putting TOO much money up front. You have to look at both sides:
1) If the flight school doesn't get any money up front, the student could easily run up thousands of dollars FAST and then leave. (I have seen it happen!)
or
2) If the student gives it ALL up front, what happens if the flight school goes out of business. (We have ALL seen this happen!)
At most schools, you have to put some money down up front. But don't put $100,000 down!