Own a cash flowing duplex free and clear in 7 yrs

I found some duplexes for sale in LEHIGH ACRES FLORIDA for $81,000.0. The amazing thing about them is that they are less than five years old and rent for $1300.0 per month. If a person were to put 25% down, there loan amount is $60,500.0. You would have great positive cash flow on a fixed 30 year loan. The more amazing thing is that if you didnt need positive cash flow you could pay off your mortgage in six years if you applied all the positive cash flow to the mortgage. That is based on todays interest rate of 6% fixed. If a person had around 85k ,they could buy four of these positive cash flowing duplexes and own all four of them free and clear in six years. You would have a net income of four thousand per month in six years. Many people in America work fulltime to make four thousand per month.