I have owned a few used Kymcos, and I understand the excitement and apprehension you must feel.
Do you work on your bikes, or require a mechanic?
Do you have a Kymco dealer close by?
Does the odometer read km or miles?
Here in the Boulder,CO area, People 250's seem to go 2000 and up... we had a nice red one up on CL for months, The sellers started at 4k and just kept going down. I think it may have ended up going around 2400.
Your market may vary however, I find that Denver/Boulder has some of the highest prices anywhere.
Here's a good blog of a guy who ran his P250 everywhere ( it recently died at 36k miles.)
I looked at the GrandVista 250 a lot as well, I loved my Kymcos. They ran great and gave me zero problems, I just kept moving up in size.