With the traditional high rejection rate at QF I’d take a confirmed job offer first and plan on paying out any bond if I got lucky later on. 30 thousand is a small price in comparison to lifetime earnings at the big Q. If you don’t have previous jet time, a few months in the right hand seat of a 737 could make the difference between passing or failing the QF sim.
Remember pilot employment is highly cyclical, you don’t want to be left standing when the music stops on the current wave. Seniority is all important too, a few places down the list can make years difference to your upgrade.