ROI on Primary

[Shannon W.]

Good Morning! 

My husband and I own a couple rental properties, and we are considering buying a new primary this year. The conversation is, do we keep our current primary as a rental or sell it? In our area rental rates are good. We can cash-flow 500-700 per month (gross) based on my calculations.  This is primarily because our interest rate is low, resulting in a low payment. Our payment is 1550, rental rates are between 2100-2400 for my area. 

My question : How do you calculate ROI on a primary since there is no purchase price, closing cost, rehab etc- is there a tool for this?

My first thought was to keep the home as a rental- we can purchase a primary with a lower down payment than needed  for an investment property. Rental rates are good, and the home is in a nice area. 

Thoughts on this ? 

Thank in advance for any suggestions/tips. :-)

Shannon