I doubt there's a single word that describes this. For me, I don't use terms like "friends" if the relationship is still transactional at its heart -- partly because I don't think real friendships are transactional, and partly because I think using such terms can set expectations in the sub's mind that are more fantasy-based and can lead to uncomfortable situations or disappointment. That isn't a put-down on transactional domme/sub relationships -- I LOVE them, otherwise I wouldn't be here on a pro domination board -- but I think it's important to stay clear-headed on the relationships.