Sorry to break the dream, but creating a marketplace from scratch is expensive, simply because 1. you have to create awareness and design an offering matching 2 different users (vs. one for an e-commerce platform for example) and 2. you can start with only a couple of users, you need to reach a certain scale to see a marketplace alive.
Also, testing the idea (and most probably iterate it) is going to cost some money and/or time.