We found that we got a ton of people emailing us saying stuff like "Hey I have a billion dollar idea: how about you do all the work and build it, and I'll give you 5% of it?". Now we just make cash investments in companies we love, and occasionally some of them are our clients.

I'd way rather write a check than do work for equity. Way simpler. I've found that when you do design work in exchange for equity, people feel like they can lean on you for free work forever.