In the course of doing rescue training, I've spent some time towing other people in their boats. It's really not bad at all once you get moving, though accelleration takes some effort. We found that it's much easier to tow a boat that has strong directional stability. For example, if you tow someone with a line attached to their bow (the recommended method), it will tend to swing back and forth, which is a pain. Drop the skeg or rudder on the boat and it follows in line perfectly, even in turns. If you decide to build a tow boat, build it with a fixed skeg or keel and it should be a breeze to tow.