Are you thinking of buying a list of email addresses? If you choose to send email marketing to purchased email addresses you’ll be destroying your domain and future emails you send will go straight to the recipients spam folder.
In this tutorial I explain how email domain reputation is calculated and the effects of having a bad domain reputation score. Buying a list of email addresses may be illegal. Sending email campaigns to purchased email addresses is illegal, against the terms of service of email marketing services (e.g. Mailchimp, Campaign Monitor, GetResponse and Constant Contact) and will ensure that you destroy your domain by getting a bad reputation score.