Best way to determine market rates for a rental?

[Ari Newman]

I'm submitting an offer an a duplex in a "hot" area of Atlanta. (Grove Park, 30318) What are some resources that you use to determine per/door rental rates? I've looked at websites like Rentometer to determine averages. The rent rolls that local landlords are posting tend to be under-market. I'm trying to lock-in my numbers and determine NOI so that I can make an appropriate offer.

Thanks for your feedback.