Leeches stay leeches as long as someone is sucker enough to continue to allow them to leech. The real answer is: Bob is now your tenant, and you'll need to go through he eviction process in court to remove him if he won't go willingly.
With that said, how about cutting Bob off? You are feeding him, providing for him, and wondering why he's staying????? If you have to have ZERO food in the house and eat out 3 times a week or keep food locked away from him, then so be it. His meds and food aren't your problem and you are under no legal obligation to provide them (unless some court somewhere has deemed you his legal guardian due to some disability). He's an adult and if he dies from not having meds or of starvation, at least he's out. As his landlord, you have to continue to provide power and water, but I'd be cutting off the cable, turning off the phone, disconnecting the internet, and locking up things like dishes, pots and pans, silverware, putting furniture in storage or whatever things are YOURS that he is benefitting from in order to give the leech as little to leech as possible.

