I learned this one from (now disgraced) real estate mentor John Beck

What John used to do was go to tax auctions, and buy the odd, probably worthless lots nobody wanted.  He’d pay $50 - $100 for these, and wait thru the redemption period and then file for title. For property tax reasons, these lots were tax assessed at no less than $5,000.

To put this in perspective in today’s dollars (this was 40+ years ago) he would have paid maybe $500 for a tract of land tax value of $35,000.  He’d then make offers on property for sale that advertised or indicated seller financing available - using one or more of these lots as a down payment (exchange) - at full assessed value.  Because many of these sellers were most interested in “getting their price” they were willing to consider the land offered at full assessed value with little or no due diligence. So if a property was offered at $500k, John might offer 2 parcels assessed value of $70k (cost him no more than $1k) and a seller financed note of $380k.  Often he was able to negotiate these deals.  The effect was that he had near 100% financing, and a property worth $450,000 at a cost of $381k.  After he met Jimmy Napier, he refined his technique based on Jimmy’s advice.  So he would henceforth include a substitution of collateral clause in the contract.  He would negotiate a below market interest rate with the seller of say 4%.  This allowed John to do one of a number of things to increase his profits.  He could offer the seller (after an appropriate amount of time) a payoff of the note  at a discounted price (say $325k).  He could substitute other collateral for the note. So, if interest rates were 10%, he could (and did) buy a note with a stated interest rate of 4 or 5 % at a large discount. So, theoretically John buys a $380k note with a 5% coupon rate for $260,000.  He then substitutes the collateral, i.e. retires the $380k seller financed note exchanged for the $380k note he purchased for $260k.  John now owns a property worth $450k for $261k!.  

These type opportunities do not occur every day. They aren’t advertised - the investor must WORK the deal to create them, and will need to endure many rejections before he’s able to successfully conclude a deal. However, these are the types of deals I’ve done many times which accelerated my climb up the net work scale, culminating in my being able to sit back and live off the interest from my hard money lending/ discounted note purchases. However, I’m getting my “second wind” and based on a successful recent “creative” note “wrap” I’ve done will probably get back into creative real estate exchanging again.