If you are referring to foreclosure auctions, that´s a different level of risk and you need to verify that it is a first position mortgage (they usually are) and set aside contingencies for other liens you might find (referenced by @Chad Urbshott). 

Here's some "light" reading if you want to learn more about this subject directly from the source (IRS):IRS: Federal Tax Liens - RedemptionsIRS: Legal Reference Guide for Revenue Officers - Federal Tax LiensIRS: Guidelines for Processing Notice of Federal Tax Lien Documents

You are referring to Opportunity Cost when you say that.  

Happy to provide a reference if you'd like.

We're plastered with adds on social media and often referred to some by friends or colleagues.

Anyone I meet with plans of moving to Oklahoma I’ll be sure to refer them to you.

Do you have any links or references to support your third point?

They replied back and said that their records only go back to Jan 1, 1974 and that I should contact the Lands Records Reference Room but they did say the last deed of record was from 1969, so there is definitely something out there.

@Richard Mukai  I'm guessing the service you're referring to through LexisNexis is the CLUE report, but you won't have access to that (unless the seller provides it to you). 

Please let me know if this is something you would like to schedule.Also for your reference, here are some other forum discussions from investors that have worked with us in the past.