I'm a positioning and messaging expert, working now and previously for several software companies in CMO type roles.

Ideally you'll want to focus on your propositions to both sellers and buyers independently. You concept is dependant on providing the mechanism for bringing these markets together, so a failure on just one side means a failure for the system as a whole.

Focus early on what works and what doesn't for each group, and what's broken in the relationship options they have today.

Nail your positioning and messaging to each specific side of the relationship, then create test campaigns and landing pages for each.

I wouldn't try wrap it up in one landing page just yet, make sure you understand what's working for both the buyers and the sellers independently first.

Good luck, drop me a line if you'd like to speak further on it!