More bangs for your buck.
Some people confuse drawing with photography. They will pose for a drawing with one person then decide it's a simple matter to be portrayed alongside another - like you would in a photo shoot. When drawing traditionally - with pen on paper it's a real drag if you have to redraw a person. I don't know why. It should be easier the second time around but that doesn't stop it from being dreadfully tiresome. Many will simply refuse. However with digital caricaturing on the iPad it's actually almost as easy as a photograph.
At a recent wedding anniversary party I was asked to combine family members with siblings and partners in various combinations but because I was working digitally I only had to draw each person once. Then it's simply a matter of combining layers.
Post event all the caricatures are uploaded to my Gallery Page where all the family members can go and view everybody's caricature and download a copy if they choose.