Hi phil,
just get a board... work with it for a while... If it's used I'm sure your not going to loose a lot of dogh by selling it... Just do some research I recommend you read that article I sent you a link to...

If you want to go mega cheap buy a $50 board that has midi from the pawn shop... buy some cakewalk on ebay and write your tunes... when done have someone do the mix down on a good board...
I think you have enough advise you need to get your feet wet... the 550 would be a great starter board... was one of my fav's
DJ