Just tell him straight out your not ready. Explain to him the extra work a puppy would be. Your the one that would be doing most of it. The cleaning after the training, house breaking etc. Women up and tell him how you feel. Also let him know that your willing to revisit the dog thing at a farther date. Sorry if I offended anyone.
You certainly didn't offend me. What you said is exactly what is in my head. I guess next time he brings it up I'll have to say something. Especially since he's been looking at English Mastiffs and Great Danes.