GET A JOB - (W2 income is sooooo much easier to qualify for a mortgage and make consistent income. 

Cash on cash is a performance metric strictly about residual cash on a single year.

On one end of that spectrum, a park with 100% PMs (park models) can look, operate and perform similar to a mobile home park. 

You will see the impact of the market tank at the end of 2018.The Historical SPY graph is similar but assumes that SPY goes up at a consistent (and in my opinion, generous) 10% annual rate.I only count appreciation if I have a new appraisal. 

I would perform an investment portfolio analysis running on your options on your real estate singularly and cumulatively.

There is a consistent process to starting any business but I haven't seen a written blueprint yet.

My intention is to find a lender whom I can consistently use for future house refinances.

For example if the inheritance is in the form of a diversified stock portfolio consisting of blue chip stocks being managed by a trusted brokerage, she should leave it there and if anything divert dividend payments only to other investment vehicles she prefers or to pay off high interest debt, but not touch the principle.

Pick the one that is the most difficult, consistently paying late and serve them with a eviction notice.  

This will allow you to look at the credit and financial situation of the Borrower annually to assure performance.