Detached 3 car garage in need of structural work! WORTH IT? ROI?!

[Matt Romano]

So my recent 2 family purchase has a detached 3 car garage.  It's in need of some repairs.  The roof is sagging, and some of the weight bearing supports are very questionable.  I'm waiting to hear back from some contractors on a few different ways to tackle it. But basically I think its going to be a pretty expensive fix to do it the right way.  2 of the garage bays were renting out for $125/mo until I had it cleared out before closing. I would ideally continue renting out the 2 bays (garage is all open / not separate stalls), and use the other single bay for myself (put a wall up perhaps). Or even rent out the 3rd if I had to.  (I'm house hacking and don't plan on staying there for more than 2 years, so I wouldn't get too comfortable with my garage space), plus the extra income is more appealing to me anyway :)  So my questions are:

-will fixing the garage structure and getting the roof done (re-shingled) have a decent positive affect on the property value? I understand the whole multi-family business model thats's the direct correlation between income and value, but aside from rent income. How is the ROI on something like this? It's something that needs to be done regardless, just curious though!

-Whats the going rate for a garage bay nowadays? This garage doesn't have electric or plumbing. But I'll add a sub panel for some lights and plugs at least.  And I was thinking at LEAST $250 for the 2 bays I won't be using.  Thoughts?  

Thanks in advance everyone!!!