@Geoffrey37
The bottom line is you can vet guests as much as is feasibly possible, you can have extensive lists of house rules, and you still may get a bad apple as you are not on site to keep things in order. Only you can be happy with that risk.
The second area to consider is local regulations and the law relating to shorthold tenancies. You need to have a very good understanding of these and in particular how long a guest can stay before they acquire 'accommodation rights' (it's usually around 30 days).
Think about who your property will attract and how many it will sleep. Will your desription read like and invite to party? Is it in a very popular location? If so, avoid 1 nighters, don't cram in too many people just for a few bucks (ask why someone is happy sleeping on an uncomfortable sofa/pullout bed for example).
Finally - as with any booking or enquiry, if it doesnt feel right then avoid. Oh, and don't forget to have the right host insurance!
Good luck - it's a big step moving from a room to an entire property. But many people do it very sucessfully