Not really at the senior exec / founder level unless it’s a highly technical solution that requires very specific skills. We’re not comparing a BDR with a junior dev here. From the OP, it sounds like the partner is more akin to a CEO and the OP is more akin to a CTO, but I don’t have all the info on the specific situation and there is a lot of nuance. If OP joined the company post revenue, 23% would be completely out of the question.

This is the right framework, but there are likely many more things he COULD bring to the table: how much money is he putting in? Does he have a loan or other risk he’s taking? Is he taking a salary? What is his background and what vision does he bring? What does he bring to the table when it comes to biz dev? It’s unlikely OP could drive this business forward without his/her partner, but the opposite is very likely true. 23% to me seems like a lot.