It depends on a number of factors but I'd boil it down to two key things to start:
1) What is your real cost to provide a free plan or trial?
2) Who exactly is your customer and what are they used to paying and who and how do they pay today?
When you say "online workforce marketplace" it sounds as though you're placing virtual workers. If that's the case, or if you're paying for the supply side of the marketplace, the question is how much can you subsidize demand?
Depending on where you're at in the process, I'd also question how much you can learn about the viability of your marketplace by offering a free version, assuming again, that free is actually a real cost to you.
I was part of a SaaS project that started charging people for early access based mostly on just a good landing page (we clearly stated they were pre-paying) and were amazed at the response.
I've also run a SaaS product that offered free trials and realized that the support costs and hand-holding and selling required to convert from free trial to paid wasn't worth it, this despite the product's significant average ARR.
You might be better off providing a "more information" sign-up form (to capture more leads) and let them ask for a free trial while only showing your paid options. I've been amazed at the lead capture potential from a simple "have questions? Click here and we'll contact you"
This is all the generalized advice I can offer based on the limited information I have, but happy to dive-in further if you'd like on a call.