She then proceeded with a full gut renovation which is projected to be completed mid-December 2017.

The building was made in 1960.We're not entirely sure how much we should project for maintenance / capex every month, in order to make the right offer on the building.What do you usually budget on something like this?

If it worked out, I could rinse/repeat.For the crowd that wants to warn me about the difficulty of being my own general contractor/doing some of the home improvement projects, duly noted.

Spending 55k with projected rents of $1500, say 500 per unit.  

Remove fourescent lights in the kitchen ceiling.

More important than the structure, however, is to take a deep dive into the sponsor’s financial projections and their historical actual performance versus their projected performance.

My question is, should I be my own GC / Project Manager and just hire subs?

Either for guidance and/or to exchange deals- You also want to network with the various tradesmen you'll encounter with your projects, like contractors, home inspectors, title companies, investor friendly realtors, hard money lenders (especially until you gain access to private money).

Being a school teacher I have summers to do big projects.  

I use Craigslist and Airbnb and have had success finding good tenants on both sites -- mostly traveling nurses and some IT professionals doing temp projects in Denver.