I think it's a great idea, seriously. There are going to be naysayers and trolls that will try to put your idea down on these boards, but most of them are just old men or cynical pricks who never had the guts to chase a dream.
Here's my advice. 1) a Mercedes Sprinter Van is expensive. For example, 2010 passenger models (dsl) with over 100k on the clock are doing over $10,000 at the wholesale auctions. Now keep in mind, these vans are Mercedes products, so they carry Mercedes price tags for service work. With six figures on the odometer, you are bound to be replacing parts sooner than later, and those parts and labor are costly. When you factor that in with the fact that you need to convert the damn thing into a living space, well, it may have just been better to rent an apartment in Colorado or Oregon for a year. You'd actually save money.
My advice would be to steer clear of German made stuff and stick to Domestic Conversion Vans. Not only will you find them for less, but they will cost less to maintain. That will allow you to budget more for the conversion, which is ultimately what you want to spend your money on.
2. This has to do with training. You can't get GREAT without a community of training partners. So throw out any "once a runner" ideas of reaching Olympic Dreams solo like a Quentin Cassidy. If I were you, I would fix up my van and drive out to the Pacific Northwest or Colorado in search of thin air, rolling hills, and a bunch of like minded athletes willing to forgoe the "real" world in favor of something far more fleeting. Not only will that keep you motivated, but it will make you a more hardened distance runner. Need proof? Check out Kenya or Ethiopia. Those guys train in massive groups year round. And the results speak for itself.
Godspeed Dude! Live by faith, not by fear...