Answer:
The premium charged for health insurance is based on a person's health, medical history, age, amounts of deductibles and co-payments and the "richness" of the benefits provided by the policy. "Richness" refers to the extent of benefits provided, the degree of choice of providers, annual and lifetime benefit limits, and other factors.
With respect to any insurance, premium is always paid in advance, so almost by definition, a premium has been paid at the time the insurance is used (if it was not timely paid, the policy would normally have been canceled). In fact, before a policy is initially issued, a premium must accompany the application.