Allowing non-housebroken dog to move in

We have rescued older dogs that were never housebroken. We have always been successful in housebreaking them within a couple of month, enough so we dared leave them home alone for a few hours with full access to all parts or the house. You do need to be diligent, give lots of praise and love and treats. Make it a good thing for them to do what you want. Go out often, treats when they go outside. Taking them to the same spot and saying go potty helps. Once their scent is there in that spot it helps. Exercise/walks for poohs unless they readily start just doing that outside. Patience -- it's not the dog's fault it wasn't housetrained. You could even try putting pads outside on the grass for a bit. I do also want to add - small dog, small bladder, will have to go out more often.