You need to be listed as an additional insured and a certificate holder.

It's a minimum 2 years before the certificate holder could apply to send it to a tax deed auction, if they do.  

Joseph, if your Solo 401k plan has a custodian, then typically there will be two signature on the documents: representative of the custodian such as Trust Officer and you as the account holder. 

In this case, if all lien holders agree to accept less than the amount owed on the debt, a sale of the property can be accomplished."

By "refi" I'm saying you need the ability to obtain financing if and when the lender calls the mortgage due after a sub-to sale, that is simply paying off the existing lien holders.

Can another lien holder like the mortgage company come in after the purchase, pay you off and take it back?

Does anyone know how a second mortgage holder comes to know that the borrower is going to be foreclosed on the first mortgage?

You can but requirements of the first lien holder may negate your ability to close the deal based on a second mortgage being done.

This does not mean the flipper never holds and the holder never sells, but by and large I find that niches = riches.

The trustee file will have a full list of all the lien holders and other people of interest that have to be notified as they have some interest in the property.