Octomom better pack a large bag -- and 14 small ones -- because TMZ has learned the person holding the note on her home is at a foreclosure attorney's office right now, preparing to file foreclosure papers against her. 

As TMZ first reported, Octomom is behind about $7,500 on her mortgage payments -- plus she owes a whopping $450,000 balloon payment which is due October 9.

The noteholder, Amer Haddadin, tells TMZ he's at a foreclosure attorney's office right now and plans on having the papers completed by day's end.

That $500,000 Vivid porn offer is sounding better and better by the minute.