Opening a HELOC on a primary home bought via Subject To??

I haven't been able to find a clear answer to this question. I'm buying a "primary home" via a Subject To deal with decent equity. The seller will obviously hold the debt/note for the existing mortgage while the title gets transferred to me. My question is, would I be able to open a HELOC on a second position lien if someone else (the seller) has their name on the 1st position lien mortgage? Once again, I'll be holding title and ownership of the home, just not the debt of the original mortgage.

Essentially, can you get a HELOC if the Subject To deal will be your primary home while someone else holds the note for the original mortgage? Has anyone been successful at this?