Artists and musicians can be hired if you want it badly enough. I had to spend over £1200 on Holiday Bonus art/sound even though I didn't have the money (I got a loan). But I made it back over five times, so it was worth it - you've got to take risks in business to get payouts. Sure, for a non-commercial game you won't want to spend any money to make graphics/sound and then finding a team to do the work could be quite hard as you'll have to find other hobbyists who are busy with day jobs and other commitments.
I can not agree with this statement any more. I have put a lot on the line for this current project and my only hope is that I see some type of ROI. If I do not, hey -- at least I have a game that I will actually enjoy playing.
Also the sound part is not all that hard. I am certainly no musician, but I purchased a copy of Adobe Audition, downloaded the free Loopology tracks, and was able to create some fairly decent game music. It needs some minor editing, but overall it was not complicated at all.
There are also lots of "production" music which is royalty free. You can usually purchase these in CD sets and it allows you to use them in video, radio, and game productions.