I have a merchant acct. for my sm. business (I am restricted to tell you what it is due to free advertising). I pay a small fee of $1.50/month + $.45 per trans and 2.5%. I am able to call in the transaction over a phone to get instant authorization. I have no electronic machine. I do have a paper machine that I can roll a card, but use it very seldom.
Like others have said, shop around. I know a guy in landscaping that takes them and hates it. I dont mind it. I guarantees you are going to get your $ sooner (unless the card is maxed.)
As for customers in the tree care side of my life, I have had them ask if we take cards. there we dont. I've never lost a job because of it that I know of. Most just ask when it comes time to pay.