LZF, 

PP's are usually set up with a minimum and maximum funding. The issuer can close with as few sales as will satisfy the minimum and can sell no more than the maximum. No broker represents the issuer, so no over-allotment, which is a kicker given to the lead broker or underwriter as additional compensation. 

Often, the issuer will pay a finder's fee to someone who brings in an investor to a PP. Very much like a commission, but one does not have to be registered or licensed as a broker or agent to collect a finder's fee.