Advance Realty Timonium
You often find that in manufactured housing developments. You can also find that in some older cities, such as Baltimore, Maryland.
In some cases--as with some manufactured housing developments--the ground rent covers a lot of different services, in the same way some condominium fees do. In other cases--such as Baltimore--the ground rent may be minimal. And sometimes there's even the option of buying the land and eliminating the ground rent.
Check with a Realtor who knows the area for more information.
Hope that helps.