Such plans are available to those who have some form of self-employment and no full time employees.

I agree with above comments that you should employ a property manager if you want these to be truly passive investments similar to the stock market.

What are your favorite sites/resources for researching list prices, sale prices, cap rates, rents, employment and demographic trends, etc?

Came across a trailer park with decent sized trailer homes for sale.

Also factor in grounds maintenance, which depending on your area may include snow removal and/or lawn care and landscaping (this can run a few hundred dollars a month depending on the size of the property).I always ask sellers for their P&L statements for the last 2 years which should show any major repairs and expenses.Regarding financing I think you nailed it and should look for more traditional financing elsewhere assuming you qualify.

In fact brick and mortar for retail has been doing exceptionally well across the country especially in the 20,000 sq ft and under box size.

When you are in employable years, the employment market should match or exceed the existence market (housing, utilities, food, cars, etc).

A good number will vary based on the current market and the size of your metro area.

@Marc PelletierFirst off your spreadsheet is hard to read due to size.  

Dwelling Size.