Good thoughts!

I think the second point is really the most important one. Even before the actual idea you should start building an audience and/or a network. It's such a crucial mistake to start a company without a relatively easy way to validate your ideas and get feedback.

However, I like to disagree slightly with your third point about making something you are passionate about. I think you should be passionate about building a business but should not fall in love with your idea or product. It's a lot harder to pivot if you are too in love with the idea, the solution or the problem.