@Jonathan Holmes, @Joe Davalos and @Michael Ablan There are a number of sites where you can direct people to get off mailing lists.The FTC has an informational site about all sorts of unwanted contact: https://www.consumer.ftc.gov/articles/0262-stopping-unsolicited-mail-phone-calls-and-emailBut the place to go for opting out of mail is The Direct Marketing Association: http://www.directmail.com/mail_preference/Most professional and ethical list compilers will run their lists the the DMA suppression each month as part of the standard list hygiene.

One of the concepts that is brought up often is “what happens when there are no more unwanted animals?”

You explained that many sellers used seller financing to sell an unwanted piece of property because that was the only way they could do it at the time.

My job as an investor would be to persuade  ( Don't know if this is the right term to use) the property owner to take less because of their situation (foreclosure, property damaged/outdated, unwanted inheritance, etc.) 

Not everybody needs the cash and not everybody owns an unwanted home.

Does anyone have any advice or an efficient way to find/purchase vacant homes, fire damaged homes or other unwanted properties with too much work/damage?

Police reports, noise complaints, discussions re unwanted gatherings suggesting drug activity, complete list of tenants and phone numbers. 

The result is unwanted interactions.

If you see more funds available, you will make that unwanted purchase. 2.

If not, most folk superstitions agree that a good old fashioned sage burning is useful for cleansing a home of unwanted spirits.