ROI on garage conversion

[Gregory Alcala]

Good afternoon to all BiggerPockets members.

I hobos this is the correct forum. 

I have been a member for a short while now. I've been reading, watching, analyzing properties to educate myself. 

I'm interested in a multifamily, currently with three apartments and a three car attached garage. The building is a large rectangular brick building. The garage sits under one of the apartments. 

I have questions to those of here with more knowledge and experience than I. 

Is the ROI or equity gain favorable to convert the garage into a small one bedroom? This would allow me to keep the current three tenants and live in this fourth one.

What would be a rough estimate to build out it out? 

Thanks for any responses!