As to whether or not there's a market for it, it depends greatly on where you are. Are there any particular attractions nearby so that you could market your flights as 'scenic', or would you just be taking people for a ride in the local training area? If you simply are taking them for a joy ride, what type of aircraft would you be using? People (after getting over the "It's old!" factor) would probably be much more interested in flying in a Tiger Moth, than in a C172. Are there many tourists coming through the area where you live? If so, keep in mind that there is usually an off-season that you'd have to see yourself through (eg. In Tasmania, a lot of activity providers close down over Winter because it's too cold for tourists to come across and play. They are trying to remedy this situation now by introducing a festival over Winter, which I think is a very good idea!).
Just a couple of things to think about.... Good luck!
