Given that the iPad has no USB ports, printers will be connected to your network. You can choose from printers that are equipped with an Ethernet port Ethernet, or ones USB that will have to be connected to an AirPort terminal.
Popina recommends printer Epson TM T20 Ethernet for its ease of use and robustness.
Popina is compatible with the following two printer brands :
TM-T20 (II) (Ethernet)