DayZ and Arma developer Bohemia Interactive will allow hosts to make money from their servers.
As of December 1, third-party DayZ servers can be monetised, with Arma 3 to follow on February 1 2016.
You need to register and receive approval from Bohemia before you can begin charging players for access, and there are rules.
Players may not be rewarded with gameplay-affecting perks for paying cash, although cosmetic perks may be handed out and walling off the server from non-paying guess is permitted.
Server owners may also sell cosmetic in-game items, and accept product placement, in-game advertising and sponsorship. Donations are also permitted, but must not be linked to content access.
Those who break the rules will have to cease monetisaiton practices or face legal action.
More details can be found here, along with links to an FAQ and the registration pages for both games.