(Unlike the flipping shows where they focus on drama and design).

If the floorplan allows you can certainly make changes that either add square footage or re-designate space (Example, convert a den to a bedroom). 

The reality of it all is that many fail to recognize that life is designed fundamentally on the idea of TIME ⏳(plant > cultivate > harvest OR sow > reap). 

Purchase price: $80,000 Sale price: $142,000 I designed and did most of the work myself with the exception of tile installation.

The El Paso county assessor is looking at changing our property tax rate designation to commercial so you are correct on rates.

But don't worry about tiling outside of the shower on the walls - that's not really needed, even in homes over $500k - purely a design choice, and the same look can be accomplished with wainscoting.

I fully funded the rehab and provided design and project management services, then (as an agent) listed the home for sale.

I'll recommend Tellus since it's designed for rent collection.

Assuming everything comes together and you are confident you can get the financing you then need to contract with a civil engineer and architect and or design build contractor to start the design and entitlement process. 

They are state specific and designed by investors and attorneys.