There's a good article here on why authors shouldn't let anyone handle their self-published books for a percentage. I agree with her conclusions; if you need to hire people to help you do covers or format or edit or whatever (and you probably will need help on some of this at some point), pay them a flat fee, not a percentage for the life of the book. You don't need someone to "package" your book for you (and she makes really good points about this often being a conflict of interest, I think). I know it all can seem intimidating when you first start out-- but really, it's not that hard.
Another thought occurred to me as I was reading this. If you have an agent, and s/he worked hard shopping your manuscript around before s/he finally gave up, I know it can be tempting to think you owe that awesome, hardworking agent a percentage of your royalties when you self-publish. But you don't. Your agent's job is to sell your book to traditional publishers. If s/he didn't accomplish that, and you wound up going indie, you don't owe him or her a percentage. If you're that grateful to your agent, then go write another book s/he can shop around New York, but don't give up any of your self-publishing royalties!