How does no cost insurance for the elderly work?

This refers to insurance plans, called "Advantage Private-Fee-for-Service" plans, that one buys to accompany their Medicare since Medicare does not cover all costs (neither do these insurance plans). Many of these Advantage PFFS plans have a zero premium, hence they are called "no cost". They can offer a zero premium because this type of plan receives compensation from Medicare directly to provide coverage; in essence, Medicare is paying the monthly premium rather than the participant.