Contrary to other comments, splitting costs is perfectly legal for private pilots under FAR §61.113(c)<p>The fact that an intermediary allows the pilot and the passengers to find each other, or acts as an escrow service to ensure payments are made, is irrelevant.<p>§61.113 Private pilot privileges and limitations: Pilot in command.
(a) Except as provided in paragraphs (b) through (h) of this section, no person who holds a private pilot certificate may act as pilot in command of an aircraft that is carrying passengers or property for compensation or hire; nor may that person, for compensation or hire, act as pilot in command of an aircraft.<p>(c) A private pilot may not pay less than the pro rata share of the operating expenses of a flight with passengers, provided the expenses involve only fuel, oil, airport expenditures, or rental fees.