Hello,
First, I recommend that you
register a domain name for the business.
Next, a business email hosting plan such as
Google Apps or
LuxSci should be selected so you have professional tech support for your email and any other business hosting.
Next, after the new addresses are setup and configured, notify your customers of your new email addresses.
After the above is complete "Dave" can create message rules that copy+forward email from business contacts to the new email addresses since you expect some of them will continue to email that Yahoo address.
This will allow "Dave" to preserve his personal Yahoo account and help to give the business a more professional look than having a Yahoo address.
to Email Questions!