Just go for it. Ignore everyone who tries to change your mind about different cameras. There is nothing quite like a Leica. If at all possible, I'd go for a BP MP in your situation, just 'cos its pretty (I've had one for a decade or so), but after that, a chrome M2 or M3: I'd go for M2 because I like 35mm, and because the M2 VF is similar to just about every other Leica ever made (reparability). I'd not want to bet on a meter lasting 60 years, but like you, I believe that B+W film will survive. The other things against M6/M6ttl are (1) rangefinder patch flare and (2) the cranked rewind. The former is very seldom a problem, but when it is, it is. For the latter, the simple pull-up style is stronger.Ignore those who tell you it can't be damaged. It can. I repaired mine in the Julian Alps with a Leatherman...
I've actually been using Leicas since I was your age (in 1969, so that's 43 years, over two-thirds of your projected plan) and still have my first Leica, a 1936 IIIa, though it needs repairing. Over the decades I've owned (asterisks on the ones I still own) A, III, IIIa*, IIIb, IIIc, IIIf, IIIg, M2*, M3, M4-P*, MP*, M8* and M9*, I've used for extended periods (weeks, months or years) II, M6, M6ttl, M7, M8.2; and I've had my hands on B, I, II, FF, GG, M1, so I'm reasonably familiar with most models.
Yours is a great idea. As you say, who knows if it will come to pass? You could be hit by a meteorite tomorrow. But it certainly WON'T come to pass unless you buy your Leica to begin with.
One last piece of advice. At your age I had the choice of art school (BA Fine Art Photography) and law school (the system is slightly different in the UK, where I was mostly brought up). I chose law because it's a degree in BS, which has always stood me in good stead. Looking back, I wasted time studying accountancy (a 'good job' and 'well paid') and teaching wasn't that good either. For the last 32 years I've been a freelance writer and photographer and I wish I'd started that earlier, at (say) 25 instead of 30. Go to a big city, because that's where the buyers, publishers, galleries, etc., are: I'd advocate London (where I started) or NY or Paris or possibly LA (where I met my wife) or SF (where my niece lives). Provincial towns are... well... provincial. You can afford to move to them (or even to villages) once you're established, but even then, you need to keep reminding buyers that you exist.
Cheers,
R.