Can I get my 3-plex rezoned to a 4-plex?

[Jon Robbins]

So I have a three unit with a basement that was previously used as a daycare center, so it is technically refinished. I'd guess it's 700 sq ft. It would definitely need some work done to make it livable, but it already has a bathroom and a separate exit and I'd like to maximize the space. I don't know much about the rezoning process but I've heard it can be a real PITA. Is rezoning a three unit to a four unit something I can reasonably pursue, and if so any tips on how to go about doing so?