One option would be to buy it in your country of origin … assuming it is cheapter there. But perhaps you are already here and that is not an option. Since you are only going to be here a year, and your investment in a laptop must serve you after you leave, be sure to only buy a laptop that has an international warranty, meaning that regardless of where you go, you can still get it fixed by the local service office. I bought my Apple PowerBook G4 in the States and brought it here, as it was considerably cheaper that way. Apple provided an international warranty, meaning that if it breaks here in Taiwan, I can get it fixed. See if other companies like IBM do that for their Thinkpads.
If you just want a throw-away cheap laptop, there are plenty of local semi-no-name-manufacturers out in the computer markets that could sell you a new laptop with dodgy support. You don’t have to buy a Dell, Gateway, IBM, Acer or Asus.
I don’t have any sources for used laptops. I would be very warry about that anyway.