Some reasons to choose the Business Model First.
You are limited by time -> Almost all online business models let you use your time more freely, but it still requires effort to become really successful. The more smart time you invest, the more money you will get. Saying that you have an actual job, or you are a student. You have normally a fixed schedule, you need a model that will fit your time better.
You can’t spend too much time doing a product, right?
You are limited by resources -> Saying you have all time in the world, but don’t have the resources to sell exactly what you want. There are options out there, like affiliate or drop shipping to sell anything you want, without owning it.
Want to try a new way to make money -> In case you love trying new stuff, you can challenge your self and make profit out of any business model!
See Business Models for more info.