My project is a site like booking.com (but not to book a trip with date of start and end) with multiple sellers, commission for each sale for me.
Each customer receive an eticket by email just after he has paid his order by credit card or paypal.
On this eticket there is some informations : date of validity (1 year from the purchase for example), name of the seller and most important : a QR CODE and/or a serial number.
So the seller can check the validity of the eticket when the customer come physically to the place where there is the event. No need to have date of start and end (like an event manager).
Sellers can check their sales, statistics etc.
Administrator can send invoices each month to sellers to be paid for commissions.