I recommend against purchasing an e-mail list for three reasons:

1.       It is ineffective:  E-mail is VERY easy to filter out or ignore. Open rates on this type of mailing are very low. How  many e-mails do you read form people whom you do not know?

2.       It may violate the very trust you are trying to build with new prospects. Effective e-mail marketing is permission based. Even if someone has opted into a list, they have not given YOU permission to contact them. You are likely to get many SPAM complaints which can affect you reputation with you e-mail service provider.

3.       Its impractical. Most e-mail service providers have a policy against using purchased lists. You want to use a service provider because they can help you get you e-mails past many of the various SPAM filters in the system. They can do this because they have built a reputation for not allowing SPAM in their system and that reputation is based on having strong policies like this in place.

A better strategy would be to partner with someone who has a list that fits your target audience and ask them to send an announcement to their list on your behalf. People who respond can then opt in to your list.