[falkensmaize]

Use your phone and spend your money on lighting and audio (mic and interface). You can make your video look very professional with good lighting. Bad lighting + expensive camera == amateur looking video. No matter how good the image is, with poor audio no one will watch it.

[sneak]

Your last sentence is super true, but the audio interface is relatively unimportant. Even onboard headphone jack audio interfaces are 10x more than adequate. Main things to focus on (no pun intended) are mic placement and mic quality.