The investors got possession of the buildings by just paying the taxes owed against them.  

Unless they're on a foundation, container buildings will be considered by banks as "personal property," and banks won't finance the main house if there's a "trailer" on the property when the next buyer takes possession.  

Likewise, brokers 'transfer' possession only after documents are recorded.

In most cases, they just don't trust the investor.What are investors trying to accomplish with "buy like rent, lease option, option", In most cases it is to BUY TIME to find an assignee or to flip the property.Here are some ideas you may want to try on for size:Write a contract of sale (I use a skinny contract, one that anyone can read and understand in a few minutes) with a delayed settlement (for as long as you can negotiate), with right of possession or if occupied right of entry), and "subject to the existing mortgage"Skinny contract of sale with a Study Period, with right of possession or if occupied right of entry.Make full disclosures 1.

The misnomer is that those payments are not the buyer/borrower earning equity in the subject property but rather more like a rental payment which only serves to grant possession and not other rights and interests in the real property itself.  

Make a lower offer subject to a reserve public auction, offer the seller a 10% hybrid (10% of anything you get over what you offered), make full disclosures, get right of possession (so you can clean the house up and show it to prospective buyers), build in an extension in the event you need more time and use banking days for settlement.

From my (non-lawyer) experience, yes, the lease remains in place (The Covenant of Quite Possession).  

County Superior Court, searching Unlawful Detainer(s)Some are listed as UDxxxx (the case number) and some are UDjjjxxxx (jjj jurisdiction xxxx case number)The last status is a Judgment and/or Writ of Possession, meaning the case is closed.If any Hearings are still pending, the case is still active.

"Your" assets need to be kept distant both from you(r personal possessions) and from each other to minimize losses in the event of a successful lawsuit.

@David DachteraYes I'm aware that if I buy the 2nd and take back possession of the property I'm taking it subject to the 1st.