Seller Finance question: Springing Liens

[Seyi A.]

Hi,

I was thinking through some creative financing structures, and a question popped into my head regarding the following structure; 

- Buyer and seller agree to a sales price of $X

- Seller agrees to seller financing in the form of a mortgage with a principal of $Y (<$X) , and an unsecured loan with a principal of $Z = $X-$Y and 10-year term

- The unsecured loan has a provision that, if the loan is not paid off by the end of Year 5, a lien attaches to the property to secure the remaining 5 years; a "springing lien"

My questions are:

1) would the sales price be recorded as $X or $Y?

2) would the unsecured loan and accompanying lien be recorded at the time of sale, or only after the lien "springs into existence"?  

And, in case you're wondering, yes there is a reason why the buyer may not want the full purchase price to be recorded as $X.  Thanks in advance for the insightful responses! :-)