[RicoElectrico]

Starting up two-sided marketplaces is an art in itself. The successful companies often resorted to unorthodox practices. Search for growth hacking. Some of the tactics are clean, some unethical and many come in the grey area.

As startups aren't afraid to operate at a loss, they could offer sellers incentives that are too good to refuse. Other than that, maybe populate the side with their own "sellers".

Then again, the specific market you listed is way way too saturated for new players at this point, just to be aware.