Duplexes, for the most part, are treated like a house (vs a condo). That said, non-owner occupied properties require a minimum DP of 25%. The required credit score will most likely be over 700 (under that, points will change your mind to move forward). Preferably you should have scores above 720. The rate depends on your score, but typically it can have as much as 3 discount points added in fees which in turn affect the rate (unless you prefer to pay the fees out of pocket. The seller can only pay up to 2% in closing costs.