Devil's Advocate on the "per diem isn't compensation, it's reimbursement"

Maybe so, but that's a semantic distinction.

This is a cash flow analysis. Per diem may technically be reimbursement, but it has no connection to the expenses incurred. So if you want to not bounce checks, it very much is relevant.

But ... if you're flying 20 hours a month on reserve and half of that is 6 hour TAFB day turns, you won't be getting much per diem.

So two months, expect something in the range of $1000/month per diem. (24/7 in training) After that on reserve, unlikely to be more than a couple hundred bucks a month.