The reason you fall under higher risk is because you are transferring or aggregating funds instead of just collecting. This means you could be prone to money laundering. The new paypal api (that's in beta, see x.com) allows transactions like this without you taking the holding/fraud risk. Its probably your best shot.

Outside of that, you could try to get arrangements with an escrow provider (like escrow.com) to handle the payment part of your transactions.