Unless you have a lot of parts hanging around, it's usually a loosing proposition to 'save' an abandoned department-store bike.
I'll admit to being a bit of a scrapper when it comes to 'found' bikes. I keep two stashes of spares; one for 'my' projects and one for any 'BSO flips' that come my way.
I'll almost always look one over; if it's not in near-rideable condition, then whether it's got any components worth salvaging. got a couple of Exage DR's and 7-sp Alivio rapid-fires that way.
I've got a pretty good stash of 2nd-hand / patched 26" shraeder tubes and a handful of take-off chains that have been 'pickled' in ATF; since tubes and chains are the most likely reasons an otherwise intact bike would get dumped. If it needs much more than that, though, I'm probably going to take a pass.