I have been approached by a local business who would like to offer their visitors the option of buying photographs of their visit and I'm looking in to the implications.

They want me take photographs of their customers or at their events, load images to my site and give these people the option of buying prints or digital downloads, anyone have any views on the legal issues?

Can I take photographs of these people in general or do I need specific approval from each person? Everyone visiting has paid to be there if that makes any difference so it isn't in a public place. My first thought was to take plenty of pictures in bulk, have a page they can log on to so it is semi-private and then they can look through and pick what they want.

Any issues with this plan? I don't want to rush in and say yes if there are likely to be problems with privacy etc.

Many thanks in advance for any advice!