A large cage with a bed , with food and water dish, and a pee pad would be perfect for training him to use the pee pad outside of the cage. I would consider leaving him in the cage while you're at work until he shows he's understanding where to go and do his business. When you're home, you could leave him out to play with you, im, but if it were me, during the early stages i would crate train him whenever i wasn't there and when (not if) he pees or poohs on the floor , or your foot lol , i would gently put him back in the crate while saying "no, no , no " for the rest of the night. It might help also to have a spray bottle with a light spray on it, and when he does make a mistake, while you're saying "no" give him a spray of water in the face so he'll be able to better understand that peeing etc outside of pee pad is associated with a negative experience. Don't worry, he'll still know that you love him.
Good luck and thanks for adopting an older dog.