I do not believe you should incorporate your company yet as there is a chance you will scrap the idea or iterate on the assumptions after analysis. I suggest you run your initial testing on a very minimal MVP to see if there is interest. I would go further in saying that you should not even allow people to pay only have them click on the payment option because at that point you know that it would be a conversion. The ONLY thing you are proving with an MVP is validation of an idea. Only make the mousetrap front end and see if you can drive users to where you want and stop. Even if you frustrate some people, it was worth it as you now know for sure people will buy or do what it is you wanted. Schedule a call with me to find out more. God knows I have done this enough times.

Good luck
Josh