A preexisting gaming machine is adapted or retrofitted to print valid tickets for a game player at low cost. The preexisting gaming machine includes a game microprocessor for controlling game operation (e.g., slot machine operation) and includes a cashout signal input. A game interface is fitted to the gaming machine and coupled to the game microprocessor for controlling ticket printing and redemption in conjunction with a central authority. A memory in the game interface stores a pre-loaded ticket validation number received from the central authority. In addition, a ticket printer is fitted into the gaming machine and coupled to the game interface for printing a ticket that includes game credit indicia and pre-loaded ticket validation indicia. The game interface controls printing in response to a cashout signal. After the ticket is printed, the game interface obtains a new pre-loaded validation number in preparation for the next ticket printing event. The preexisting gaming machine is also retrofitted with a bill validator and ticket reader in order to redeem tickets, without making any changes to the game controller. Thus, the casino's investment in the game is preserved, while ticketing capability is seamlessly added to the game at a fraction of the cost of purchasing new games.