Converting single family to two-family

[Mary Grace Viterbo]

Hi! I want to convert my garage and the bedroom above it into a rental unit. My garage is located in the back of my house, attached, but it doesn't have an access to the main house. Above is my Master's bedroom with a walk-in closet. No bathroom though. I have a separate driveway there as well, that's why I thought it's a good idea to do this. How much do you think it would cost me to do this?