JohnW,
Members of this site has discussed rental restrictions in the past and will likely do so again in the future. There are varying opinions and not one statistic (at least that I know of) how rental properties affect home values.
If the property isn't properly maintained (be it by the owner or the renter) and it looks shabby (need of painting, obvious disrepair, overgrown lawn, etc.) then it's likely that potential buyers may not want to live near that property. This may lengthen the time the home is on the market. Lessening the pool of potential buyers may also force the seller to lower the asking price.
However, the amount of crime, what school district the home is in, property taxes, available jobs in the area, commuting distance to available jobs and many, many other things also affect property value. What matters to one buyer may or may not matter to another. Since there are so many variables, there are really no statistics.
The only issue with rentals, due to laws enacted because of the housing crisis, is the HUD limit on number of rentals. Since most mortgages are resold, it's mainly Fannie and Freddie that purchase them and they must abide by the new regulations. Therefore, lenders typically use those same regulations as one of the factors in determining if a loan will be made.
When I last looked, the ratio was 50%.
Here is a link to the
HUD mortgagee letters If you are considering rental restrictions, the best I've seen was prohibiting rental of the property during the first two years of ownership. This tends to keep investors out but minimizes the impact on those owners who desire/need to relocate from renting. Of course, you also need to have hardship clauses.
The counter argument to this would be - would you prefer to have the property rented and maintained vs. being left to stand empty because they can't rent it?
Hope this helps,
Tim