Your bank can give you the best idea, but you probably don't need a "real" merchant account yourself unless you're doing a lot of volume. What most people start with is a service that has their own merchant account. they sell you a psuedo-merchant account.
Fee's vary by volume - number of purchases per month, high, low, and average purchase cost, type of product - physical or intagible - e.g. is it a mountain bke, or a download?, the way you confirm the cc info/customer, and the number/percentage of chargebacks. And also if you are a "real" business - e.g. legally - and if so, for how long.
I resell for e-payment and they're pretty good from a resellers viewpoint. I also like ikobo and 2checkout. Leaning more towards ikobo no recent problems in the past year, low fees, nice api, good charge-back policy, and easy access to the $.
ikobo and 2heckout would be on my A list for someone just getting into e-commerce. e-payment is a little more involved. I like e-payment for recurring billing, but 2checkout, and I believe ikobo have both got new capabilities in that area.
All payment services have had problems art one time or another. ikobo, 2checkout, and paypall seem to have put most of them behind them. Paysystems is going through a bad time right now, and it would be best to avoid them - IMHO.
EDIT: BTW - $ savings on cc fees by being a "real" business" will often cover the cost of getting set up as an LLC within the first year given a moderate amount of sales.
Edited by dpyers - 09 January 2005 at 6:46pm