Other forces become the dominating market factor.Real estate values are inversely proportional to the debt service.

I've noticed that many expenses, such as utilities and cleaning, don't seem to increase proportionally with gross income like those cabins in Smoky Mountain National Park.

If it is just him the house is likely out of proportion to his needs so you might get extra tenants.  

With the Baton Rouge flood last year where over 25,000 homes were flooded (the final numbers aren't in yet) for a total population of about 350,000 in the area, the proportions are similar to Houston's 150k flooded for the size of the metro area. 

You can buy multiple houses instead of one, and although the rents are not as high they are higher than you would proportionally expect.

I personally want to know more than cap rate on investments, and care more about how much time the deal will take up in proportion to my returns. 

Use that ratio to determine what proportion of your cost basis is improvement, and then depreciation that (the 27.5 years).  

TLDR, you can only take a loan out proportional to what you put in it and everyone has the financial ability to put in that which they have the capacity to do.

Usually you would compact the dirt as you go.

It is the job of every investor to manage, among other things, the proportion of yield to risk they want in their portfolio to get the best returns without lose of capital.