Marketplaces are famously difficult to start - even Uber just started with black car service in a handful of cities and expanded from that. Find a trusted network of mules as your supply-side and expect to lose some money as you bootstrap.
You should already know what your largest city-to-city routes might be at this point, so why not focus on economy of scale there? If you need to rent a cube van to make it happen, do that.
it's a great reminder that Uber wasn't a 2-sided marketplace to begin with, just an on-demand black car service, and Travis drove early on. The marketplace model came later, copying Lyft, more as a low-cost expansion strategy than a business model.