Some of those points are valid (#1 especially). But when you run a business it's important that all parties are happy and feel like they have a fair deal.
You need to ask yourself that 6 months down the line, when the other person really isn't contributing much because they can't, and you're working long days sweating, working hard and putting a career on hold, and you've got 50% equity, are you going to be happy? It's not going to be a sustainable relationship for very long and has a good chance of being doomed to fail before you've written any code.
Like culture, marketing, market validation, generating press buzz, interviews, recruiting, and so forth. If the idea guy can't do a lot of those business-y things, you don't have a business so the 6-month question is premature.
I don't think it's premature, a lot of people will want a product (MVP) before they go ahead and formalise the entire thing. You're going to be the guy doing all the work in that department. Up until the MVP is developed there's really not much else to do.
Pretty much everything you listed is most effectively after you actually have a product.
Up until the MVP is developed there's really not much else to do.
As a guy that straddles the line between "tech guy" and "business guy" (I've done both of them), my opinion is that there is a lot that can be done before the MVP is developed. In fact, if the business guy isn't out validating what the tech guy is building from day one, it is almost guaranteed the MVP is going to be wrong and/or it is going to land with a resounding splat.
As the business guy, my job was getting out, meeting with potential customers, understanding what they would buy, what they wouldn't buy, and why. My job was getting early interest in our idea that could translate into (eventual) early use of the product. My job was making sure we understood who else was in the space and how we were going to differentiate our product.
In short, if you practice "throw some code out and start selling", you are going to have a really hard time getting traction.
Wouldn't you want to see that the idea guy had done his legwork before even thinking about MVP? I sure would. The lines-of-code to hours-talking-to-people ratio in the early weeks would be something crazy like 1:400.
You need to ask yourself that 6 months down the line, when the other person really isn't contributing much because they can't, and you're working long days sweating, working hard and putting a career on hold, and you've got 50% equity, are you going to be happy? It's not going to be a sustainable relationship for very long and has a good chance of being doomed to fail before you've written any code.