Alot of how they look depends on how often you breed and what you feed them. I have 2 mommas in each tub and just rotate a male or two through them. But my rats are way spoiled when it comes to food. They get a lot of variety. Nuts, cereal, fruits and veggies, bread, ensure, oatmeal and of course the rodent block. And mine are in the house so they get cleaned alot too.
I was just wondering if you really think you are in a "pet rat " market and are you going to purchase fancier rats right from the start or not. Most people dont want just normal colored hooded rats. I personally really liked the siamese rats so almost all of my females are those And I have a really dark colored male so I get hugely different looking babies. Just my two cents...
Good luck!!