Tax Liens

I have seen many infomercials hawking “how to” courses for exhorbitant fees on how to invest in tax liens and earn 18% or so.

I have done some research and it seems legit but what is the real story? There must be downfalls. What are the real risks? Has anyone invested in these vehicles?

Invested in what–in the “how to” courses, or in the tax fiddles? :confused:

Invest in the tax liens