If you get a rescue dog, it will probably already be trained, so the carpet will not be an issue. Some dogs will "mark" their terrority once just to let other dogs know it is their domain. I have a very big dog and he has a hard time walking on wood floors, I have to have throw rugs down so he can walk from one room to another. He slides all over if I don't have the rugs down, the pads of his large feet are just to slippery.
NormaBeth