Should I sell to current tenants?

[Lisa Raimondi]

My current tenants want to buy the property and i'm wondering if I should sell. 

Property background: 

SFH bought 15 years ago as a primary residence. We moved out of state and turned into a rental and in the first few years it was breaking even. Our original intention was to keep property as passive/ fixed income source once mortgage is paid. We just refinanced to 15 yr term and got cash out to purchase another investment property (now we owe 160k but worth 350k). With our next rent hike in a month we will cash flow over 500/month.

Now our tenants want to buy. Since I'm a newbie investor with only 2 properties, I'm looking for some input and ideas I haven't yet considered.  Thanks!