Ask HN: How long should a partnership wait before legally organizing?

I am in a group with 4 members. I'm a developer on it - we've agreed to an equal 25% split regardless of whatever expenses we personally incur before organizing (pretty small stuff, a $10 subscription here and there - but also some medium stuff, like paying a contractor a few grand for illustrations). Now we are about ready to think about launching and selling product - I was thinking we were going to be testing by giving away licenses for free to relevant users - but it seems like the plan is to charge. This is fine because it's not too shoddily built for what I'd call a market-testable prototype - but I know that this means there's going to be potential liability introduced. Also in terms of just protecting our interests and ensuring nobody can try to grab for more ownership when we do organize is important to me. I like working with these teammates in general, but we have clashed more than once - so it's not beyond the ralm of possibility that things might not be amicable at that point in time. When should I put my foot down regarding organizing legally? Should it be before we launch to paying customer? Should it be before we even test with customers? Or should I just chill out and wait until we're making enough money that we know the fees aren't wasted?