Sometimes it's cheaper to have a homebirth, but not always (In my case my insurance would have paid for the hospital birth minus a $75 co-pay but a homebirth was so important to me I was willing to pay over $3000 out of pocket).
I'm assuming you don't have health insurance, right? If not and you are pregnant, you more than likely can apply and receive state assistance (WIC, Medicaid, etc). Have you checked into that through your local county or state? You should be able to find info in the phone book or even call any OB/Gyn office and ask for the numbers.
There is so much to research and plan for when you find out you're pregnant. I love homebirth but I think you should only do that if you really want to do it, not only just for financial reasons.
We have a sub-forum here devoted to pregnancy and birth (and then you can post under "I'm Pregnant" - they even have a pregnancy resource thread) and the people there will more than likely have much great advice and information for you.
http://www.mothering.com/discussions...splay.php?f=19
If you can't find what you need in that forum, just ask. Everyone is helpful and I promise you'll find plenty of moms who have been in your situation and will have good advice.
Good luck to you. I hope you have a healthy and happy pregnancy.