Warnings for 1st Time Complete Gut Renovation DC Row Home

[Frank A.]

Hey BP, 

My wife and I are getting relocated to DC this summer and the only way we can get everything we want in the city is by performing a "live and flip". We're going to buy a fixer with a 203K construction loan and will do a complete gut renovation. We are nervous about this because these homes are all early 1900s builds. We've never done something so old before hahaha. 

We plan to open up the main floor and add a half bath. The upstairs we'll create an in-suite bathroom for the master and add an additional bathroom (if there's space). The basement we plan to finish as a studio with full bath and kitchenette, "apartment"/Mother-in-law suite so that we can rent it out and house hack. 

For the experienced DC rehabbers, what kind of surprises in these renovations should we prepare for and how do we know if a contractor is prepared for them? Thanks in advance.