Find a place where you are allowed to smoke. If he lives above you there is a VERY good chance you will get evicted for breaking your rental agreement, Since one of you will become complacent, and he will find out. If you sign an agreement to not smoke in HIS apartment, don't smoke. You are only as good as your word to other people. *edit* If you are in an legal state, province, territory, country, etc. I am sure you can find a 420 friendly landlord. If not, it would not be smart to chance it.