Hey Sean,
This is a pretty loaded question with so many variables. If it was me I'd be looking for something with low miles, something that appears to be well taken care of (like parked inside or mature owner) records of maintenance, ect..
If you're planning on taking it on long trips I would stick to a lower mileage bike like under 15k miles.
I have a bit over 38k on my 2000 KLR right now and other than some oil consumption it's running a great as ever. I got it at 11k and it was using oil then too. It was not well maintained by the previous owners, but with the low miles I just went and baselined all the maintenance. I've been solid with replacing oil and other fluids regularly or as recommended by the owners manual. I wouldn't hesitate to take it on a long trip right now. I even rode Baja last year with 37K on it and did over 1K miles with 800 being off-pavement. I flogged the heck out of it and it just kept purring..