( * Just FYI, Home Depot now has real marble vanity tops in stock for unbelievably great prices--not carrara, but a type of marble called Arabescato Venato, which has both gray and beige and/or brown veining, so it can work with older beige and almond/bone colored tile, (like mine) too!

But the vacancy/ collection loss risk can eat up these "paper profits" pretty fast, along with the older housing stock issues in general... which just run higher on maint. 

I'm probably equal between US real estate and US stocks, then with a few international stock funds thrown in, then I also hold some cash in several of the main world currencies.

Warren Buffett said if the stock market is truly efficient, he would never be a billionaire as he bought stocks of companies the market grossly undervalued.

There are several good senior only complexes that might work, in addition to the regular condo stock.

I tend to read books on business and stock market investing.

They said I would be dead before I collected first month's rent!

Dave Ramsey made millions through creating businesses, buying rental properties and investing in the stock market. 

(A 2 gallon would suffice, but I had a couple of the 4gall in stock for apartments).

This isn't like the stock market, where all 5 beds generate a certain average income, and all 4 beds are similar... it varies a LOT.. and it's almost completely dependent on the owner, or the decisions the owner makes about their investment.