"Marketplace startups are often considered the hardest software startups to build, because you have to create two markets at once. They work best with frequent and inexpensive transactions (from which you can reasonably take a 20% cut)"
2 sided markets get started by buying one side of the market. This is why this model is very expensive to bootstrap. You typically start by offering free or very discounted services to the consumers and pay the difference to the producers until you have captured the consumers and the producers pay you for transactions. All the while you have to mitigate disintermediation, so that producers can't bypass you to access the consumers outside of your market platform.
2 sided markets get started by buying one side of the market. This is why this model is very expensive to bootstrap. You typically start by offering free or very discounted services to the consumers and pay the difference to the producers until you have captured the consumers and the producers pay you for transactions. All the while you have to mitigate disintermediation, so that producers can't bypass you to access the consumers outside of your market platform.