Since you bought your property as a foreclosure, most likely you didn't have any type of disclosures or guarantees about the number of legal units. A simple bit of research from your Realtor/Lawyer should tell you whether or not you have a "Legal 3" or a "Legal 2" unit. However many legal units your new property has, is how many you should rent out. There are many people who, for lack of a better term, "slumlord" and rent out non-legal units. As with any illegal activity the choice is up to the individual, however you may want to research the implications of liability of breaking said law. That said, some people in your position, rent out the two legal units and live in the non-legal unit themselves. This may be an option for you as you take all the risk onto yourself. This is by no means a recommendation! Be safe, not sorry!