Renters in your own house... separate areas?

[Matt Liu]

Let's say you buy a single family as an owner-occupant, with the goal of having a couple renters to defray the monthly bills. But let's say the town does not easily allow conversion from singles to multis anymore. Can you install a kitchen and bathroom in the renters' part of the house, and even have a separate locked entrance to their area, perhaps just the whole upstairs for example?
Can you even have in the lease or "house rules agreement" that they cannot come into your part of the house? Or do i not have the power to designate which area a "housemate tenant" can and can not go?