Help with garage conversion

[Aaron Ford]

Hello! I’m wanting to get started in real estate and I have a pretty cool situation. The home I currently own has a two car detached garage with a small office and a full bathroom. The garage is on its own electric/water/ and separate address about 200ft from the house because the prior owner used it for his business. I had the idea of converting the garage into an apartment, but I’m not really sure where to start. Conversion cost is something I don’t know much about. I’m located in a rural area in the Carterville, IL market. Any help is appreciated.