ya. Even in the first Karate Kid movie Daniel-san was getting his ass kicked with this method. I don't even think buying a bag is going to really help you much. You will just tire yourself out with bad technique. No one there to tell you to keep your elbows in and your chin tucked....no one to throw back at you when your hand drops etc. You will just teach yourself badly and then get progressively worse, develop bad habits and then become harder to retrain when you join a gym later. I second the 'bug your friends' system. I am generally pretty happy to help people out when they want to start training, and always looking for new sparring partners, so, if you happened to live in Vietnam, I'd be pretty damn useful

Otherwise - look at the cheaper martial arts...boxing and judo at local community centers are probably going to be your cheapest options - and are both great styles in their own way. Maybe tkd or karate as well, which I am a bit wary of as a general rule, but I suppose if you find a good teacher, that trumps style arguments. If you are a student, then also check out what your college has as martial arts options too - that tends to be way cheap. Slight twist on that if you are not a student, maybe the local colleges offer public training in the student classes for slightly higher fee (but probably still way cheaper than a fight gym). edit - just saw OP's most recent post - ok...nothing in your college...ignore that! but note, there is no fight style on earth that you will learn in five mins a day. edit2 - random dumb idea - is there anything you are particularly good at that you could craigslist/college noticeboard barter? ie 'teach me to box and ill teach you Spanish' kind of thing?