I guess I'd think the same whether it's your full time residence or a temp incall.
1) The animal should be in another room when the guy arrives until you figure out how the guy feels about it.
2) The animal shouldn't be whining or barking in the next room.
3) The room shouldn't smell or have too much fur. You'd think this would be common courtesy, but far too many pet owners can't smell the smell any more, and overlook the fur everywhere.
4) I'd love to play with or pet the dog before or after the activities, but put it away before the fun starts. Remember that some people are afraid of dogs, even small, cute ones.
5) Allergies. If you were providing from your own home, the guys would have to put up with it or not visit. I see no reason this should change if you're using a separate incall.
6) If the animal is well behaved and in the other room, the guy need never know. However, that could still be a problem if the dog moves around and makes some noise. The guy might think there's another human hiding in the next room.
7) Some guys will be upset no matter what you do. As long as you follow the points above, up theirs.