My retirement plan, whats yours?

[Lee Cruz]

Early 40s investor here with 6 sfr. I plan on retiring 15 years from now. We can buy 4  sfr a year with a purchase price of 100k each and brrrr each one. Plan on stopping at 20. My partner and i make 150k a year each. 

Plan A: is to get to 20 single family houses in 3 to 4 years and start paying them down or

Plan B: start paying them down after 10 next year. We would be able to pay one off every year. But keep purchasing the 4 a year till we get 20.

I understand the argument of just keep buying more money with leverage with cheap interest rates, but we like the idea of free and clear. Less stress, less risk is more appealing to us. What are you retirement plans and any suggestions about mine? Thanks.