​How do I split equity in a bootstrapped SaaS startup?

I built an MVP and have one customer paying $250/month. On Y-combinator I was looking for a commercial co-founder met a guy who has bootstrapped 2 companies, each to a successful exit. (Since one of his startups is still known by certain technical subs years later, I created this throwaway account. Also, I don’t want to self-promote.) He has also worked for several pre-revenue funded startups and has a good network. He’s urged me not to raise money until we get much more revenue, if we raise at all. He’s willing to match my hours and work part-time so that I can keep my day-job.

We’ll both work on the project equal amount of time. He’ll help me with everything, other than the technical work. He’ll use his network of part-timers to build out the product until it can sustain full-time work. However, I’ll have to do the selling for now since I am the inventor and SME for the industry that I’ve applied AI to. (I work in law or banking or accounting or similar industry that I don’t want to disclose, and taught myself how to program AI.)

This being my first startup, I don’t know how to split the business.

How much equity should he get?
When does he get it? The product and company have a long long way to go and he clearly knows the steps but the journey will take a while.

EDIT to answer forum requirements

How long has the business been operating? months Where is this entity/business registered? USA Is geography a factor in the partner you seek? Why/why not? No Is this an online-only (no physical presence) business? yes What is the proposed arrangement for the partner? Are you offering them shares, will they be a director, paid as a contractor? What did you have in mind? equity only What about capital? Is this partner expected/required to invest? no Which currency? USD What are you looking for from a partner (skills) AND what is it that you bring to the table? see above Will the partner be able to provide input/suggest changes to the entity’s constitution? yes Do you have financial records & projections? Will you share them with potential partners? no