Looking for some advice on possibly lending in 2nd position

[Chris Policicchio]

Hello BP'ers!  I need a little help/advice.  I've done a decent amount of private lending, but I've always been in first position.  I have an opportunity to lend to someone I trust, but I'd be in second position.  The purchase price is $350k.  In 1st position will be the seller, who is financing $250k.  I'm being asked if I can lend $85k.  ...so the buyer/borrower will only have $15k in the deal.  So obviously being in 2nd position and the buyer only having $15k in the deal isn't great.  Like I mentioned, I trust the buyer and I have lent to him before.   Ignoring the $15k for a min, what can I do to protect myself in 2nd position?  I read a bit about options/agreements where I could make payments to first position if borrower stops payment, but some of the threads were hard to follow.  Does a personal guarantee buy me much?  Anything else I can do?  I'd appreciate any/all thoughts.  Thanks!