data on rental volume

[Brandon Robinson]

I've been following BP for a while, but I'm still in the preliminary ("save and study while I continue my day job") stage, while I consider beginning in real estate investment with a primary goal of building a rental portfolio. One question I had was whether there is available data to easily determine the volume of rentals in a given area. 

In other words, say I'm looking at a SFH property that looks like a deal, I do the analysis, find the median rental rate in the area, and believe that I could acquire the property and rent it out at a rental rate that meets or exceeds (cashflow) the expenses. However, it could be in a neighborhood where people simply don't rent - maybe it's upscale and people tend to purchase rather than rent, and the "median rental value" is based on only 2 rentals in the neighborhood over the last 12 months? This could result in future difficulties with vacancies - not because my rental price is wrong, but simply because there aren't a lot of renters looking in the area. For due diligence, is there data readily available where I can see the *volume* of rents in a particular area (beside just driving around)?

Hope this question makes sense, and look forward to any available advice.