Seller Second Lien Financing Explained

[Colby Wise]

I was recently listening to a great MHU talk from Abraham Anderson "0-100 lots..." who brought up the concept of seller second lien financing, but I am unfamiliar with how cash e.g. downpayment, is exchanged at closing (and escrow). Can someone please walk me through the process in detail? 

For example, let's say a private lender accepts second liens with the first lien being at 75% LTV. Normally on a $1,000,000 park the downpayment would be $250,000. Now if the seller carries $125,000 what are the steps of this transaction?

Clarity on this would be quite helpful as looking at a number of parks and I'd like to aim for a bigger park but has short-term (< 6 mths) liquidity shortfall and prefer not to sell assets or raise from friends/family. This could be a great tool for arsenal!