I just get what I feel like getting. I don't really expect all of my dogs to get along. They get limited play time together here and there, but I don't need them to get along 24/7 free roam in the house. One female is spayed and rest are all intact.
Recently got a female pup - now that my fosters are all gone, I had 2 permanent females and a male, but that didn't fact into my decision making. I wanted a nice female cause that's what I wanted - was not based on my other dogs at all.
Same goes for any fosters or temps. If they get along with the permanent dogs, that's fine. If they don't, that's fine too. I don't expect all dogs to get along and have the resources to separate as needed.