I am not a banker or mortgage lender but from my experience of looking at this same scenario i would say the numbers probably won’t work for you. When you refinance the best you could do would be to refinance at 80% of the current value Most of the mortgage brokers I have been talking to require 30% down on an investment property and also @ 6-7% interest. A better scenario would be a heloc if your bank would do one since the property you are borrowing against is a rental. Not sure if you are old enough to remember the housing bubble bursting about 12 years ago but a lot of millionaire investers moved into the poor house My advise to you is to tread water until you save enough to purchase a second rental and not put your other house at risk
