How to value a garage refurb

[Ian Jaeger]

Hey all, recently bought a property here in Dallas and am doing some work to it prior to doing a house hack / airbnb thing with it.  The majority of the house was actually in pretty good condition, but the garage was a wreck.  

I'm trying to set up a line of credit to smooth out the cash flow for the refurb and one of the things I'm struggling with is how to 'value' a garage refurb.  Intrinsically, there's value to turning an old, dingy, rodent-infested, unfinished dirt-catch into a clean, well-lit, nicely finished space complete with a stainless workbench with sink / drain, cabinet enclosed, stacked washer/dryer, matching cabinets around a large gun safe and the water heater.  And Epoxy/Poly-U floor coating.

Does anyone have any information on what a comparable set of properties with the only difference being a clean, finished garage versus an original, unfinished space is?

-Ian