What Slim said. 'Is this rat a pet' - Yes it is a pet for sale. If it doesn't sell it may not be a pet, but what do you think happens to pet store rats and hamsters that stick around too long? I've sold some rats as pets. Actually the people felt a little bit like they were 'saving' the rats from me, which is fine. They were pretty cool about it... I explained I don't feed live, raise them in uncrowded conditions, treat them as pets, give treats, etc. My experience has been with people who are more curious than upset.
I have some VERY rare and fancy rats, so I'm sure the people who buy those might ask more questions. The ones that are going up for pets get put in a tank and socialized and put in a high traffic area of my house so they aren't scared of people. I think most people ask because they're wondering how socialized the rats are when they get them.