There is no need to buy a crap guitar to improv a thing as natural as finger strenght. Just play guitar for increasing amounts of time, and your fingers will adapt. No matter the guitar. If I play a thin neck super strat such a Jackson Soloist for 3 hours non stop, its going to make my fingertips red and I would be able to see the dead skin flakes... Getting a crappy guitar will discourage you playing because your trying to play phyically, not emotionally.