My suggestion?

Buy a miata for under 4k. ;p

Seriously?

Why are they driving an M3 and you're paying their bills? HELLO!!!!!!

You need to have a "sit-down" with the in-laws because money matters are serious business. Work out a monthly budget for them. If they still manage to dig themselves into debt, its out of your hands bro.

And on a serious note. You shouldn't be making such large purchases/financial commitments when starting a new job. You HAVE TO ASSUME that you're extremely dispoable during the first year of employment.

3 month probation? maybe. I wouldn't feel comfortable buying that car till I had at least 10k put away in dispoable income.

25k and I'll fly out this weekend. =)