Best resource for checking rent comps?

[Justin Welling]

Howdy BP community. Currently trying to check average rent prices in different areas of my market (Pittsburgh, PA area), particularly for privately owned single family and town-home units, and was curious if anyone knew of a great resource for doing so? I'm aware of the obvious sites such as rent.com for data on available units, but what about a resource for units that are NOT currently available (i.e. currently rented out by a tenant/units rented within the last year)?

Thanks for any feedback.