Charging extra for more tenants

[Matthew S.]

I have a new property in TN that will be available for rent soon. It's 975 sq ft 3 bd / 1 ba. The interest I'm getting is from families where there's a mom, dad, and 4 kids. I don't discriminate against kids, but 6 people seems like a lot of people to fit in such a small house. 

Can I have a base rent rate and state it's for up to 3 people, with a fee ($50/month?) for each additional tenant? Has anyone done this?