I have had no experience with this, but I just would not even try it. Kinda just rubs me the wrong way. Just my own opinion,
Gary

Wow. Sounds like it is not worth it.
Ed

Most of those leads aren't what I would call quality leads.

I would not recommend it... Facebook and other social entities are monitoring this kind of behavior. If caught, you can be banned for life from Facebook for life as well as other social platforms. Here are some links. Check them out, then decide for yourself.

http://www.digitalupstart.co.uk/social-media/social-lead-freak-review-this-very-popular-software-will-see-you-banned-from-facebook/

https://www.quicksprout.com/2014/02/19/how-to-steal-your-competitors-facebook-fans/

https://www.quora.com/The-audience-for-Facebook-Ads-can-be-targeted-or-defined-by-a-particular-email-list-If-I-have-an-email-lets-say-johndoe-facebook-com-will-my-ad-display-for-that-particular-user

https://www.reddit.com/r/socialmedia/.../facebook_uid_scraper/

Inspiration 1

I never recommend purchasing leads. If the leads were ever as good as advertised then they would be too valuable to sell.

That's just my opinion my Friend,

Tony