About the UM vs FIU dilemma... That is a tough call. UM is ridiculously expensive. You pay full tuition for a year, and then after that, you only pay a sort of a la carte, but you are definitely right in the ballpark of $25K. FIU would be substantially less, but, I would caution that FIU doesnt exactly have a national reputation, so I have no idea what their stats are for any med schools including UM. There were some pretty damned smart people though in my MCAT class who were taking classes there. But I have no idea about their stats and couldnt even guess. My goal is to go to UM too, and the way the premed office made it sound is that coming out of UM, I'd have a good shot. Many of the profs (particularly biology) are affiliated with the med school, and they take a good number of people from the school and just generally have a sense of what the postbac there entails. That may be total nonsense- unfortunately I wont find out for a couple months... But before I moved down here, I had no idea I could take this at FIU. No clue if I would do it differently now to save some $, but that wasnt a huge concern at the time I decided to go- so that is totally different for everyone.
Affordable housing though, there is plenty, and Miami now seems to be a pretty good investment. Rentals are fairly low, and south of the coral gables campus you can get pretty good deals. I lived in coconut grove when I first moved there (this was unresearched and I had to find a place in one day), and you're better off finding places (particularly entire houses) in South Miami/Kendall.
On top of that, I didnt think it would make such a difference, but Miami is just a fantastic place to live. Even weeks on end confined to a library, you're still happy to get out of bed in the morning.
Research, shadowing, etc, all a phone call away. Really easy to get work at Jackson doing whatever you want.
So, in summary, it's a tough call. I moved down here very uninformed and pretty spontaneously, but I am so glad I did it. At least I am now. Of course, I dont yet have any results in terms of admissions to show you guys, but hopefully it will work out. Good luck with postbacc, wherever you go. It's tough, but I found it extremely satisfying.