How to price a rental?

[Bryce Caron]

My wife and I are in the process of purchasing a duplex in Portsmouth, NH to use as a buy-and-hold multifamily rental. My question is how to go about setting a reasonable market rent? So far I have spoken with someone whom lives in the town to get their opinion, but they don't have an experience beyond being a renter. The most they have said is some of my numbers look reasonable.

A strategy I was trying to use was to find similar quality apartments online to calculate a dollars per square foot and then average them together to get an idea, but I am not sure if this is a good idea.

Any thoughts?