finding emails for free using google

if you google:"site:linkedin .com {occupation} {area} @gmail.com"

it will give you a list of people with that occupation in a specific area that have an email in their bio

for example:"site:linkedin .com real estate agent los angeles @gmail.com"

will output the emails of real estate agents in LA

do with this information as you will...

That's basic Google Dork.

You automate this extraction by coding a Python script or use a tool like Scrape box to extract data