Figure 10-12% to be safe.Any utilities costs like water/sewer or house electric? 

Thats why I thought maybe building her a home where she never has to worry about old plumbing or electrical or foundation problem.

Another little trick I used is to look at electricity bills.

Typically doesn’t comply with footing/foundation requirements, vapor barrier in the slab, need to run water to the unit, you’ll need to comply with a number of electrical requirements, insulation, separating the garage space from dwelling and many other requirements.  

Other than high dollar tasks like strategy/vision, negotiation, drafting agreements, plumbing, electrical, etc I do now realize I'm only saving $15 or $20 an hour and need to ask 'who else can do that?' 

I am paying thousands of dollars for these vacant buildings for water, gas, electricity, oil, insurance, taxes, sanitation etc.

No structural changes, plumbing, electrical, etc foreseen, just cosmetic updates at this point. 2 main questions.- Is there anything wrong with continuing as it has been for the foreseeable future? 

The best part is I borrowed it from another electrical contractor who uses it for his six-figure and up jobs.

And RV parks often won’t allow them unless they can meet appropriate length, width and electrical and plumbing requirements, which can add thousands of dollars to the home’s cost.""

Institute RUBS or other claw-back provisions if the electric bill has become a debilitating expense.