Go to the bike repair shop, without your bike, and tell them what kind of riding you want to do. Then ask about used bikes. As mentioned before, brake pads and cables are an easy fix, but I wouldn't even consider paying someone to do major repairs on a department store bike. Once you start tearing into a low end bike, it's like opening a can of worms and soon you can have far more into it than it's worth. It sounds like you want a BMX bike anyway, so sock money away for that rather than putting it into repairs on a bike that is your second choice anyway.