There are three common ways a marketplace makes money, and founders often treat the choice as something to settle after launch. It is not. Each one requires a different thing to exist in the software on day one, and switching later is a migration, not a setting.
Commission on the transaction
You take a percentage of what moves. The model everyone pictures, and the one that aligns your income with your users' success.
What the software needs: the money has to pass through you, or at least through something you control. That means holding funds and releasing them, refunds that recalculate the fee, and a commission rate that can differ by category, by seller, and by promotion — because within six months it will.
What it costs you: the largest build of the three, and the strongest incentive for your users to meet on your platform and pay somewhere else.
Subscription for sellers
Sellers pay monthly to be listed and to sell. The money between the two sides may never touch you.
What the software needs: far less on the money path, and much more on proving value. A seller paying every month will ask what they got for it, so you need visible statistics — views, enquiries, conversions — from the first month, not the second year. Dunning, plan changes and proration are their own small project.
What it costs you: your revenue stops tracking your users' success. A seller who had a bad month still pays, and cancels.
Listing or lead fees
Sellers pay per listing, or per introduction.
What the software needs: the least of the three, which is why it is a reasonable way to start. A wallet, a balance, a top-up, a charge.
What it costs you: it is the model most easily gamed on both sides, and it makes your marketplace feel like a directory unless the leads are good.
The one that suits an early platform
If you have no supply yet, the answer is usually: charge nothing, for now. Getting the first fifty sellers to list is a harder problem than monetisation, and a fee on an empty platform solves nothing.
But build as though you will charge commission, if that is where you intend to end up. A wallet, an order with states, and a place for a fee to be calculated cost little to include early and are painful to retrofit once you have live transactions and real balances.
The version we build
Our twelve-week marketplace build assumes commission with funds held, because that is the shape most of the projects we are asked about end up needing. In the platform we run, the rate is one system-wide setting, but it is copied onto each order at the moment the order is created rather than read back from the setting later. That is a small decision with a large consequence: changing the rate tomorrow does not quietly rewrite what you earned last quarter.
If your model is one of the other two, say so on the first call. It is a cheaper build, and we would rather scope it honestly than sell you a money path you will not use.