Buying a used XP or any other saw can be a crap-shoot. The OP doesn't mention unlimited funds or a high enough budget to buy new. I work on these things for a living, and you can really get into some money if you end up with a saw that has P/C, crank, bearing, seals, or other major issues. The support is also poor on non-existent for some models, unless you are willing to put a $30 China made P/C in one, which I REFUSE to do here, it's OEM or I send it back with the owner.
Sort of related but just had a friend of mine drop off a Partner cut-off saw in really nice shape that didn't run. He just figured it needed some carb work and fuel system cleaned out. No, BIG chunk missing out of the piston and huge gouge in the liner. Guess what, NOTHING available anywhere for that model, new or used. Even worse his brother paid a guy $175 for it!.......Cliff