Fit is First. Test ride the bike. After stand over, pay particular attention to how comfortable you are regarding the reach, saddle to bar. If not just right, but very close, it's probable tweaks can be made. You'd need to verify with a lbs. In any case, get the bike checked over before buying. $800 max.
As to the mileage, that is a non-issue pretty much, with the exception of wear on the gear teeth and tires, as long as all else works smoothly and the cosmetics are passable.
It's not uncommon to spend considerable $$$s customizing a stock touring bike to fit the particular needs of the owner. And it can take a lot of miles to figure out exactly what those needs are. Reach, gearing, bars, saddle are the usual components that get changed.