The Everlasting Drink is a strictly roleplaying based merit, it costs nothing, as it has no significant uses, although slightly more disadvantages.
No matter where, no matter when, the character with this merit can always find a drink (alcoholic only). Friendly strangers might buy them a drink at a pub, they may find a half empty flask they had forgotten in their pocket, or any number of other strange occurances. The only thing to remember about this merit is that Adventure! is set during the American Prohibition of Alcohol, and so could lead to any number of embarrassing and illegal run ins with the authorities.