I think the main concerns would be to make sure that any girl was housetrained and/or good in the house. Most of the time, the housebreaking isn't a problem, but one female that I got as a mature SchH3 couldn't retire to be a house dog in my house or any other--she couldn't be confined--she'd chew through doors and was terrible in crates--she was also extremely bitch aggressive. She lived out her life as a kennel dog in the biggest kennel I could give her (often a 20x24 grass kennel during the day and smaller concrete, roofed run during the day). I walk my kennel dogs at least twice a day, so it wasn't like she was just shoved out to wither away by herself, but it wasn't the life I would have liked to give her.
The other concern is to watch for aggression with small animals and/or other dogs. And meet the girl, of course, if possible, to make sure she's a good fit. Many, but by no means all, will be bitch aggressive--although that may become less of an issue after they are spayed and no longer have that biological imperative to protect their future pups.
In general, they can be wonderful companions--they tend to have very good manners, some training to a higher level, and excellent discretion with small dogs and kids from their time spent mothering. They certainly deserve the best retirement they can get and if they don't get along with other residents of their current home, a "retirement home" can be a wonderful option.