Did you have a written lease? That's the first thing to check for requirements on leaving. If not, in my area you're only required to leave the premises in reasonably good condition - usually meaning the same way it was when you moved in minus normal wear and tear. So if you stained the carpet, it's your responsibility to have it removed; it the carpet wore out through normal use, not your problem. Anyway, I'd check with an attorney (usually the first consultation is free) or the local government (who license these landlords). Some areas also have groups for renters that handle disputes either free or for very low costs.