Started shopping for used...

It will be a couple months before I'm ready to purchase a used T250/350 high, hopefully extended, but I'm starting to watch the market closely now. Its difficult to tell how much volume there is out there, and I see a higher % of low roofs than anything.

But I have never shopped for a 1yr old vehicle before and I am not sure I understand the market too well. The first question I always have in the back of my head is "why are so many people selling at less than a year and taking such a loss?"

Second question is "does mileage really matter when we're talking about 8k vs 14k vs 20k?" I'm not even certain that mileage is effecting prices in any predictable way.

And third question is how much are these used Transits in demand, as in, will dealerships negotiate? Or is it one of those things where if I see it advertised what I want, best snap it up and don't try the old "hmm, lemme think about it" walk out trick.

Sorry if this isn't posted in the correct place, but it seemed to fit. And any advice appreciated...my car shopping experience has always been a much more open-ended process with lots of input from Edmunds, KBB, etc, if you know what I mean.

-B