BRRRR my detached garage?

[Samuel Leatherwood]

Greetings Bigger Pockets universe. My girlfriend and I recently bought our first home in the Colonialtown North area of Orlando. For those unfamiliar with the area, there are many duplexes, townhomes, and detached multi-family properties interspersed with single-family homes. Our property is zoned R-2a with a detached garage behind the main property. We are walking distance to many restaurants, bars, coffee, grocery, and more. I am hoping to get some advice regarding a detached garage conversion/addition to turn my single-family home into a house hacking situation. 

Okay, so I know I am not "buying" the garage as I already own it but I was hoping to analyze this as if it were a BRRRR deal. For example, I would hope to rehab the garage into a 1 bed/1ba 500 sq foot unit, rent it out, refinance my home, and then (hopefully) pull most of my construction costs back out of the deal.

I am hoping to get some feedback. What are the pitfalls here? Is there a version of this approach that makes more sense? Is my capital best deployed elsewhere? Would love to hear from agents who sell homes in Colonialtown, agents who sell detached multi-family in Orlando, or investors who have experience in this domain.