Section 8 single family homes

[Ryan White]

I'm a new investor and have an opportunity in front of me that I'm looking for advice.  I have someone willing to sell me 2 section 8 homes (4 BR homes both built in 2009) and they have been rented out to the same families for the past 6 years.  One tenant pays the full rent (voucher plus their portion) and the other doesn't pay anything (just the voucher is paid).  The zillow estimate for these properties is around $200k, city assessment is around $185k, and he's willing to unload them both to me for somewhere between $140k-$150k each.  

I'm looking for advice on section 8 rentals (experiences, lessons learned, recommendations, etc.) and an understanding of whether they typically appreciate well or not.  My assumption is that I'm getting them under market value (based on zillow and city assessed values) and my numbers indicate that they'll both cashflow more than $200/month.  However, I'd end up having to do a cash out refi on my current house to obtain the capital required to purchase them.  Looking to be informed on section 8 purchases before I pursue this offer.  Note that I'm currently more in favor of pursuing this offer than not, especially if I can get them for $140k/each.  

Thanks!