How to figure market price?

[Laramie Hiebner]

I recently purchased a triplex that has three tenants currently and in one unit a tenant is planning on leaving in 2 months how do can I figure out what the market price is for my area? The unit is in the basement renting at $320/month which way to low! I'm hoping to add some features to the unit such as painting the walls a more attractive color and adding more light so it doesn't seem so dead any other tips or thoughts?