So in most cases, I've found that very low bids are not an opportunity but a warning sign.   

That’s one of the reasons why I told the original poster about having his sellers sign a disclosure  stating that the loan staying in their loan could affect their DTI and ability to get a new loan.If you’re saying that a mirror mortgage will offset the DTI on the underlining loan of the seller that is very interesting.

Right of recession:Buyer and Seller may rescind within 3 days of signing contract all all EM must be returned this is a blanket rescission.If Buyer or Seller never get the Disclosures and sign for them they can cancel right up until the day of closing with all EM returned. this should level the playing field keep bad actors at bey and give Buyers and Sellers some rights if they think they have been hood winked.

Cold calling, mailers, signs, google/Facebook, RE meetups, RE agents are all ways a whole sales would find deals

See what the $19k was for first, it may have been neccessary, but still that does not make it ok for them to do it without a signed CO.You can ask an attorney a few questions using sites like Avvo or Rocket for not much $$$.

As I studied earlier, the first thing you should do is marketing, then get a call and do a property analysis to understand if it's profitable for you, then meet with the seller and sign all the necessary papers, then if there is a debt in the bank we do a reinstatement quote, then do a title search to check if there are any hidden debts, if everything is fine we look for an investor or flipper and sign an assignment of contract with him and wait for closing to get our money.

With a mortgage the borrower signs a Note and a mortgage creates a lien on the property to secure the debt which must be recorded in the public records to provide notice to third parties. 

Seems 98% of them just want to take a picture holding a big key sign and promote their business on social media.

As noted above, a cash deal with all capital liquid in an account today is going to be taken much more seriously than a financed deal or a syndicated deal.  10% EM hard at contract signing and a 45 day close with no extensions will be taken more seriously than 3% EM hard after 30 days, with a 60 day close and 2x 30 day extensions.  

You may be able to lean on the title company if they missed something, but generally if the deal closed and its not an issue of material disclosure or title or something its generally your issue now, the owner doesn't really have an obligation to comply if they closed according to the CD you signed.