You should only purchase a list of “suspects” on one condition: you plan to reach out to them via phone, personal email or direct mail first and give them a reason to sign up for your email list.
Here’s why: First, pursuing random people who haven’t given you permission to email them is against the law. (You may wish to read about the CAN-SPAM Act in the U.S. or Canada’s Anti-Spam Law.) Second, you would probably spend a lot of money buying a list and might accomplish nothing. Think about it. How much attention do you pay to emails from companies you don’t know and/or have never heard from?