As part of my consulting work, I occasionally found myself inside homes, sampling their air or their tap water. I met with a large number of dogs.
Most of the dogs I've met have been pretty happy to see me, whether they were small yappy dogs or large overly enthusiastic dogs ("Oof! Down boy!"). I did meet with one mama rottweiler who was guarding an elderly relative who was alone in the house, and the dog made it very clear that I was not going to go upstairs. Fortunately, I didn't have to go there! The only ones that I really worried about were a pair of extremely skittish and very young (think full-grown but not filled out) rottweilers that had recently been rescued.
My mother has a paralytic fear of dogs, which was understandable because she was attacked by an off-leash guard dog that had been trained to attack without warning. She transferred that fear to me when I was younger, reinforced by some bad experiences that I had. Note to owners of large dogs: if your dog associates stuffed animals with "doggy toy", then you'd better make damn sure your dog is under control so it doesn't aggressively chase after random toddlers on the playground, rip their favorite stuffed bear out of their hands, and mangle it. I didn't get over my fear of dogs until I was in high school and finally outweighed the average large dog.
Entering a house with the clear owner's permission usually means I won't have any trouble at all with the dogs (or other pets). I've been fortunate in that I've dealt mostly with residents and homeowners who are more or less ok with my presence, so I haven't had dogs set on me or been chased out...yet.