Is AirPrint free

Yes, Apple AirPrint is a technology exclusive to all Apple products. 😉

Only Apple products will print via AirPrint, but it is not an exclusive technology. If it were, then you would be required to purchase a printer made by Apple.

This is not the case. Many printers models (Xerox, Canon, Brother, etc.) support AirPrint. You just have to make sure the one you purchase includes AirPrint.

Setting it up also requires a router. You can't print directly to an AirPrint enabled printer. It first has to be connected to your router either with an Ethernet cable or wirelessly. Then your Apple devices will be able to see and print to the device.