How do you structure equity splits in a 3-founder startup pre-seed with unequal contributions?

"Two technical co-founders (one full-time, one part-time) and one business co-founder who sourced the initial client. No vesting agreement yet. We're raising a $500k pre-seed in 60 days. What split structures have worked in similar situations? What are the landmines we're walking into by delaying a vesting cliff conversation? Looking for people with direct founder experience or startup legal/finance backgrounds."