owner financing question

[Mike Jennings]

hi there,

I'm about to get my first property under contract using owner financing by 10% down and all payments going towards principal for 20 years! 

My question is the previous owner still has the first lien on the house until the note is paid off; so could I then resell the house to someone else and place myself as the second lien on the house, similar to how a bank would collect interest on s traditional mortgage? And then if for some reason I have to foreclose on the lien, would I simply pay off the first lien and now own the house free and clear? 

I hope my question makes sense - any help would be appreciated. Also feel free to ask clarifying questions!