Starting an Niche Online Selling Platform

Let me start by saying, this sounds "crazy".

My wife is thinking about having an online selling platform for a specific niche of antique products that she knows very, very well. She was asking me how hard this would be to setup. I was like yeah, are you crazy? So a site where you allow sellers to sell this niche product line and charge a small fee to have a seller account as well as a very small fee for items sold.

There are many other sites like this, but for a large range of products. Obviously ebay, etsy, rubylane, etc come to mind. Thinking about it, not sure it's doable for me unless there is a theme or template that I could start with and build from. I am in the technology industry, but this feels overwhelming.

Clearly this type of venture would require a lot of time and funds to start with. Would need the ability for sellers to create an account, have their own store front with inventory management, payment options for buyers, calculate fees, etc. I am sure this is just scratching the surface.

The more I think about what is involved, the more I am thinking she may want to think about something else.

Any thoughts you have would be appreciated.