cheapest best bang for buck is gonna be an SR20 S13 Silvia.
Cheap to fix
Cheap parts
Cheap panels
can fit lotsa skyline parts and newer silvia parts for better performance. plus you won't be haggling against guys wanting 180sx's to put strawberry kits on to make into another show pony / weekend drifter. S13's a cheap and nasty, and they may give you Hep C, but goddamn that burn is worth the ride. buy it, beat it, fix it, beat it some more.