My DB response comp was in the same condition, $50 from a local bike group acquaintance but badly beat up. I put new brake pads, did the best I could to lube the cables and refresh the drivetrain, gave her a thorough cleaning and some kenda kross tires for riding on the road. there was good off-road rubber on the bike, so I saved those for when I decide to get muddy. fenders, lights, and a trailer hitch, and I have myself a cheap decent winter bike/tourer.

my point is that I was able to do all my own labor and honestly a good lube/cleaning was all that was needed to make this bike more than ready to ride. I know what I bought and I know what it can, and more importantly, can't do. for $50, you literally can't go wrong, and if you make it passable you can probably quadruple your money on craigslist. if that's the case, fix her up, ride it for a while, and if you don't find a use for it, make some money.

if you don't do your own labor, then its probably not worth it. flip it on to someone else who will do something with it. you don't have to take a loss, but you won't make much.