u have to borrow from banks. don't u have to pay mortgage? don't u have to pay RE taxes and other expenses? why do u think mortgage rate is about 5% now? to make sure banks have most if not all the rental income.
if u pay with total cash, 30-year Treasury bonds yield 4.75% now. AAA corporate bonds yield even more. why bother with all the hassle of housing if u can buy bonds and collect coupons?
remember, all assets compete with each other. it's the future expected return that counts. the after-bubble housing market now is particularly difficult, with supply much more than demand, disillusion with houses as investments among good part of the population, baby boomers retiring, and increasing interest rate expectations.