Setting Rental Rates

[Wilfredo P.]

I'm new to the PB community and this is my first post. 

I've had an investment property for about 10 years. Half of the time I was living in one of the units and renting the other two units to family members, below market value.

One of the units just became available and I'm having a hard time figuring out the "going rate" in the area (I don't want to leave money on the table). Is there a good resource (online/in person) where I can get comps or appropriate rental rates in my area? 

The house is in Lawrence, Massachusetts.

Any help will be greatly appreciated.

Thank you.