You can get into a new rental property for less than $20,000. Of course, the more money you put down the better your cash flow. If you put down 20%, you will very likely experience positive cash flow.
But, let's assume you get 80% financing and only bring $32,000 to the closing table for down payment, closing costs, and pre-paid expenses. Under this scenario, you will probably run positive cash flow annually (after accounting for your Homeowner's fees, insurance, taxes, and property management). Compare this to an investment in the stock market where you earn 10% per year for 10 years.