They might consider Paypal. Or even an electronic payment gateway
(link LinkPoint, Verisign's Payflow, Authorizenet.com) with an internet
merchant account.
With them keying in their transactions, the transaction will probably
be downgraded to non-qualified and they will be charged around 2% more
for that transaction. And depending on their contract they might be in
violation of that contract if they exceed the amount of keyed
transactions.
If they plan on doing more than around $1,000 a month, they might
consider an internet merchant account. This will also give them a
virtual terminal to key in transactions as well for about 2.19%.
Emailing the credit card information is not a good idea. You can but
you need to set up encryption keys so that the email is encrypted and
if intercepted by a third party, cannot be read.
-Corey
http://www.loudcommerce.com/promo/google.asp