Hey, before you buy some Indian Runners have you had a look at any other breeds of ducks. I myself own some Khaki Campbells. Simlar to Indian Runners infact they were made by corssing Indian Runners and Rouen ducks. Khaki Campbells are just as good layers if not better than Indian Runners. Their arn't really any differences in what you need to do to look after them and the space they need but they are a bit shorter and fatter and are just another breed of duck you could look into. Here is a link to a site on Khaki Campbells Welcome to Berigora Farm - Growers of Organic Produce
I know this was a bit off topic but oh well you should be fine no matter which of those two breeds you get.