If possible don't fall into the trap of trying to maximize what they will lend you. That's what has got us into this mess in the first place.
I feel for those guys who are on a bum deal having to pay for type ratings, line flying etc and need to borrow more still to afford a first house etc, but try to be realistic and start on the property ladder with something that's well within budget such as an apartment. Even if it's not in the most exclusive area you can always up sticks once you climb the job ladder.
The problem with flight duty pay is that you only get it when you fly, so it's not guaranteed. Also, the tax man takes less of that money as it's your expenses, but we all know that any day now he's going to start picking off a lot more from that pay - after all you are a privileged employed person and must support all the stay-at-home lazy scum that are struggling to save enough benefits to afford that latest plasma TV and Xbox etc.