I did essentially that.
And I hope you do it, because man, THs need places!!
The more considered and discussed in advance, the better. It's okay to sound "difficult" or "hard to live with." Those are subjective ideas, and it's best to weed out soggy people and get ones in that are up for clear conversation and solid communication.
I would discuss these:
*can they have pets? what kind? what roaming options do the pets get?
*are they using your house's power? if so, is your house able to provide that? how much power can they reasonably consume?
*what levels of sounds from inside their place (electric guitar? TV on full volume?)?
*what access/use of the yard do they have?
*BBQing, etc?
*how much space around the TH is for their personal use (potted plants, bicycles, etc)?
*is smoking in the yard okay or no?
*where is their mail going? (e.g., if through a slot in your front door, what's their access while you're away?)
+1 to everything in writing, and definitely check what laws will apply in your area. Not just the ones for a TH being allowed, but the ones governing rentals. (Is TH on your property considered a legal tenancy? If so, what laws are in place? If not, what does govern it? Etc.)