Ask HN: What's the most informal way of splitting equity with pre-llc clients?

I'm in the process of launching a small SaaS dev agency with a friend (done this semi-successfully in the 2000s, much different landscape today though), and I am interested in pursuing the idea of taking an equity split with clients who can't afford development, but we believe they'll be good at selling their idea given a solid MVP. Anyway - I know that some of these people won't have an LLC or other organization set up yet, but I might want to work with them if there's a reasonable way of agreeing to a partnership in the event they form an organization, or if they generate any revenue. Is there any reasonable way of doing this, or does it not make too much sense? I remember pioneer.app doing something like this at one point - where the equity was promised beforehand.