Which CRM to partner with for use by my clients?

I'm in the middle of launching a new business at the moment that does some typical things in atypical ways.

One of the things we want to do is to bundle our offering with a CRM, and have some level of integration with our offering – whether that's just a simple embed of the CRM forms, or a full API, that doesn't entirely matter right now.

What we do want is something with a free tier that can be used to get them started, but that has an affiliate/partner program so that if/when those clients upgrade we get a clip of the ticket (preferably for as long as they continue to subscribe).

Minimum requirements are a solid sales CRM, with modern pipelining/kanban style deal stages. Ideal would be to have decent marketing tools available as well.

Very interested to hear this community's thoughts on what's out there!