Our two were 6 years old when we got them. Snoopy was partly housetrained but Susi had spent all her time in a laboratory, living in a tiled room with no outside space. Training her was hard but she got there in the end. Took about a year before we could trust her, and several carpets! Even now if she is upset she might have an accident but basically she is fine.Snoopy 'marks' strange places, like hotels!
You have to watch them all the time at the start. The moment they get up open the door and out-even in winter. Good luck, you'll manage it.