I owe about $150k on a good rental property. Currently it is slightly cash-flow positive. I have a plan to pay off this mortgage in 6-8 years. Once the mortgage is paid off, the goal would be to take 100% of the rental profits ($12k/yr) to counteract my wife stopping working full-time.
OR, would it be better to put this same amount of money towards my Betterment acct for retirement, while paying my normal, low-interest rate mortgage on the above rental property?