If you actually mean building a platform like Ebay or what not. Sure, you can build it. It won't be cheap, but that's still the easy part. The hard part is finding customers, content, managing everything, etc. If you build it, they will come is not something that is actually true. You would need a significant budget and a large team to pull it off.
I now have a second platform in a closely related niche. Think, waitress/waiters. On my platform, around 40% of the members who work in that first niche also have an interest in the second niche - but no platform existed in that niche. I created a separate platform for that second niche, and created a notice to everyone who had indicted interest in that second niche, on the first platform that this second one existed. The second one now has more DAU’s than the first one after just a few months on plans launch marketplace
Basically, my main question is if I went with a custom built marketplace through hired developers, how would they build the marketplace? Would they use a service like Webflow or Bubble? I understand that a custom built site would cost more, I'm just thinking long term. I want to be able to control all features I add to the marketplace.