In the 11th part of her series on how to build a blog, Andrea Wren discusses using the blog to sell a productRight now, I'm working on the creation of a product for my blog Butterflyist.com. This will hopefully make me my millions. Or at least, if it's popular, a tidy regular income."The great thing about having your own product is that you spend the time it takes to create it once, and then it can continue to make you money for months or even years to come," says Glen Allsopp, my blog teacher from ViperChill."Imagine having a job where you only worked for one month and your employer paid you that monthly wage for another 11 months? It just ...