Any experience on freelancers marketplaces?

Hi everyone,

I am an actuary (data expert in the insurance industry) and I realised that there was nothing for my peers to find freelance missions. Since freelancing / on-demand services marketplaces are growing, in all dimensions (dev, design, home services, etc.) I am convinced my domain is a niche market where it would be a great opportunity to propose an upwork-like platform.
But I am keen on listening to other indiehackers who might have built similar projects and would have some feedbacks to provide me with (e.g. is there a minimum market size to justify the need of a marketplace, which features are mandatory even for an mvp, etc. anything from technical dev to marketing strategy would be appreciated)

Looking forward to hearing from you guys.