For marketplaces, it helps to use a SaaS PSP that supports split-payments or payout routing. That allows a single checkout charge, then automatic splitting to vendor accounts and your commission. Key is to check the API for payout scheduling, vendor payout thresholds, and handling refunds or partial refunds correctly. In tests, I looked into how refunds propagate to all parties. Clear fee and payout reports saved a lot of headaches when we onboarded new vendors.