Hi. The main worry would be making sure the wheels are sturdy enough. I would recommend a steel mountain bike or touring frame. Higher spoke counts typically make for a stronger wheel. I think you should be ok with a standard 36 spoke front wheel, but in a rear wheel I would look for something with 48 spokes. 26" wheels are stronger than 700c, so if you go with a bike that uses 26" wheels you might be able to get by with a smaller spoke count, maybe 42 or even 40. Another way to make a wheel considerably stronger is to use an internal gear hub. This allows for the wheel to use spokes that are all the same lenght and that makes for a stronger wheel.