@Benjamin Shaw
Holding a note (mortgage) are basically the same thing. They are a lien from a certain position on a property. Maybe it will help if i take a property i recently purchased and give you an example of how to use this. As in all instances, definitely do not try to do this without consulting and using a qualified real estate attorney.
@Ben Leybovich please step in if the following example does not follow your meaning. You're certainly a more qualified and experienced teacher.
Example: I want to purchase a 4-plex. I have already evaluated the deal and recognized it is a great deal. And I have multiple exit strategies at the end of it. I know that I do not have the financing. So I find a private lender who is willing to finance 60% of the property cost, but only if he has a first mortgage (note) on the property.
Now I have 60% of the total property financed. Next I approach the seller and say, "I would like to buy your property, and I can give you 60% of your asking price up front, and I will need you to give me a loan for the other 40% as a second mortgage against the property"
The seller may not like this. But, you can help "sell" the idea to the seller in this manner. "If you (seller) would do this, you will still hold a lien against the property that I intend to manage and handle all of the day to day operations and maintenance issues. You will no longer have to be involved. Plus you will be receiving the asking price (or whatever negotiated price can be agreed upon) in full. With basically 60% of the money up front, and interest plus the balance on the rest of the money." .. I might also tell the seller, it's kind of like he refinanced his property to get 60% of the value out of it, and he still has no more burden of running the day to day operations.
There are a lot of different way of "selling" the seller on this concept. And, you will probably have to. Most sellers want all of their money up front. But, many sellers realize that there aren't a lot of buyers for their particular property. And getting 60% up front, plus a 2nd mortgage and interest on the other 40% is an interesting option.
I hope that helps. Ben is certainly a better teacher than I am. I would recommend really diving into your studying of his and other real estate teachings before making a leap of this kind.