I have an older HP non-wi-fi printer connected to my Apple Airport Express wireless router which includes a USB port. This makes the printer available with my wireless network which I've used for printing wirelessly with my former Apple PowerBook and now with my MacBook Pro for years. I'm now able to print from my iPhone and iPad as well.
You need to have the printer connected to a wireless router for your wi-fi network, or purchase a printer that is wi-fi capable and if you do that you might as well purchase an AirPrint compatible printer which doesn't require a wi-fi printing app purchased from the app store.