Yes it's possible. However, after I updated to IOS 9, all my USB based MIDI/audio devices stop working with my IPAD mini.
Most audio interfaces will require a powered USB hub since the iPad can't power them on there own. You'll also need a USB to lightning adaptor. As for the type of interface to use, I'm not sure. look on line for info. There's a good chance any interface will work as long as it doesn't need any special driver to install. Another words, if the device will work with core audio on OS X, then it will most likely work with IOS. Also, the companies that make the daw software you want to use normally has a list of interfaces they've tested with there app on there website. check that out as well.