Audio recording equipment for imac

[mufstufnstudmufn]

I am new to this game, can anyone tell me about an audio editing device that would be cheep for my imac. I heard about the Roland UA30 USB Audio Canvas Interface, is it any good? if you dont know about it see here.
http://www.edirol.com/music_equipment/usb_audio_products/ua30.html

if you can send me in the right direction i will be creatful.