When you get a Home Again microchip, you pay an initial fee. That puts your pet in their database, and gives you full coverage for 1 year. This full coverage includes 24/7 medical assistance to a hotline, they assist you if your pet goes missing (contact vets and shelters in your area), and I think there was something else.
After a year you have the option to renew that full coverage, or just stick with the basic free service which is keeping your pet in their database.
If I log in to my HomeAgain account, I have my 3 kitties as well as a bunch of kitties I fostered and adopted out recently whose owners haven't changed their information to their name. The recently chipped kitties have "Full" service next to their names, and the date the full service expires. My kitties have "Limited" service, and it gives me the option to upgrade to full service. I don't see the point, so I'm sticking with the basic service.
So please don't let the idea of an annual fee discourage you from microchipping your pet - you have the choice of whether to pay for their full coverage.