KC my little boy was a rehome who came to me when he was 2 years old. He was never house trained and I think his first family gave up trying to teach him.
When he came to my home I watched him like a hawk and took him out side once every hour. I walked and walked him around the field until he would pee and then I gave him hugs, rewards and tons of praise.
Over and over I kept up the hourly walks for probably the first 2 to three months and then he finally got it.
When I can not watch him (while working)I keep him gated in the kitchen with a scented pee pad. He rarely has accidents now...only if I leave him to long with out a break or if he knows it's raining
spoiled boy.
You just have to be patient and remember these little ones have tiny little bladders and need to pee more often than bigger dogs.
Good luck with your new family!
Snow