If someone is playing and has only 9 villagers - it could be days. As long as the town with the villager hasn't visited a town with 10 which in theory should clear the villager floating in the aether
As long as the town where you want them has an open space.
I had 9 villagers for at least a week when I got a StreetPass villager - it was a total surprise!
So if my friend had someone move out a few days ago, as long as I'm the first to street pass them and have an opening, I would get the villager? Thank you for the help btw unfortunate things happened recently :/