I had a licensed locksmith re-key all the doors, he charged about $15 per key hole plus a one-time trip fee. Now I only have one key, which can open all 8 locks. He told me that some cheap locks can be opened very easily, so if you decide to buy locks and replace them by yourself, be sure to avoid the cheap ones. He said the brass locks on the doors of my 60 year old house are pretty good compared to what we can find in local stores nowadays.