Paid cash for the land, and I have started to work with an architect, surveyor and septic designer on the build out.

If I am going to sell it, I will repair or replace the dry rots, paint exterior, and repair the roof.

The modern features and amenities can attract renters, and energy-efficient designs might help keep utility bills down.

For every dollar put in, the deal is designed to generate the equity multiple dollars out.

If that baseline average is an acceptable figure, then go a few notches up from there with your design and amenities and you should do well. 

Then if you are only looking for cosmetic flips then you limit your targets and increase competition because every wannabe HGTV, realtor, interior designer, contractor, handyman is looking for the same easy flip.Its doable but lots of strategy and organization, hustle. 

Look for the Certified Cost Segregation Professional (CCSP) designation, which indicates certification by the American Society of Cost Segregation Professionals (ASCSP).

In contrast, STRs work this way intentionally, by design. 

Your build out cost will be less competitive for the elevator systems, fire sprinklers, exterior parking spots- unless you do drive through load zones, and exterior wall surface.e. 

BiggerPockets is full of resources designed to help you along your journey, whether you are just getting started or a seasoned investor.