I built an ecommerce marketplace 10 years ago. It's quite complex in terms for mature that a marketplace offer today by not just feature and backend capability but also UI UX.

I worked at a small VC-backed startup that tried to create a marketplace for algorithms in a small niche. We were the platform that enterprise customers trusted, and we standardized access to proprietary algorithms. We subsidized the marketplace by implementing algorithms ourselves and offering steep discounts to early enterprise customers.

I saw right away that it would take years to build up a two-sided marketplace, and we did not have enough money for that runway. I created a skunk works that did product-based consulting. That generated meaningful cash flow but was not respected as strategic by the board.

The company became a zombie for a long time. In the end, it was forced to be acquired to make the initial VC money whole.

My advice is to build fast to get to a critical level. Then be prepared to drip-feed it for a long time to see if it becomes self-sustaining.