First of all, Merry Christmas!
Second of all, this thread is driving me crazy and now I feel compelled to respond. I apologize preemptively for being a buzz kill.
Let's get this out of the way, of course you can find deals on the MLS. People have at least a little motivation to sell or else they wouldn't have listed their property. Of course.
But you need to get ridiculously lucky, or be willing to take on a property with so many issues that everybody else (can be literally hundreds or thousands of other buyers) aren't willing to do it. If it's that bad, then you will be taking on either a HUGE headache and/or a HUGE risk.
Let's talk about the example that was praised above. Property listed for $240k, buyer negotiated down to $215k and got a "deal". Is this really a deal???? NO
Option 1 was to sell for market value of "230k-235k". Let's run the numbers, and I'll even give the benefit of the doubt that you don't have interest/loan costs since you claim you're purchasing with cash.
Buy for $215k plus $3k closing costs. Assume hold for 3 months until it sells. Utilities $500, taxes $1000(?) insurance $300. You collect $1200X3 = $3600 in rent. Sell for (best case) $235k. Commissions at 6% would be $14,100. You'll have another $1000 or so in closing costs on the sale.
Total credits = $235k + $3600 = $238,600
Total debits = $215k + $3k +$1800 + $14,100 + $1,000 = $234,900
If you used hard money then you lost money, for sure, but let's assume you didn't. You just tied up over $220k for 3 months to make $3,700, best case. This assumes there's no maintenance issues, the renter pays you all the rent, and you get the max asking price. If that's a return that excites you, cool (and maybe you plan to do FSBO and save commissions?), but chances are not everything will go perfectly and you'll end up losing money. You have to factor in your risks as well as the potential reward.
Here's the other thing, you buy it for $215k cash and do nothing, then expect to get $235k. First of all, what are buyers going to think? Hmmm, this sold for $215k a month ago, the pictures look the same, it must be worth $215k! Even worse, appraisers will (correctly) think the same thing. The property was presented on the open market to hundreds of potential buyers, and the seller took the best offer presented to him which was $215k. Nothing was done to the property, and how much did the market change in 1 month? (probably not much) Most appraisers will say it's worth $215k and use you're last purchase to justify that price.
This is all not to mention who is going to want to buy a house for $235k with a renter in it paying $1200? Rent to value is abysmal, less than .5%, so most investors won't accept that. If it's a primary home buyer, they won't like that there's a renter in there.
Sorry for the diatribe, I really am. I feel like a Grinch. I just could help myself.
Let's bring this back to the original post, regarding why people want off market deals. If it's truly off market, and I mean that you've contacted the seller directly and are the only buyer who knows about the deal (not a "wholesale" deal that's listed on the MLS), you have a MUCH higher chance of getting a real deal. The definition of going under contract with a seller is that you have the highest/most acceptable terms that a seller is willing to accept. If you're the only buyer, there's zero competition. If the property is "on market", then literally thousands of buyers could have looked at the property, and dozens could offer on it. If you win the contract it literally means you were the highest bidder. By definition, in a liquid market with plenty of buyers and sellers (on-market), whatever the property sells for is market value. It's only in an illiquid market (limited buyers and sellers, i.e. off market) where a deal can be made below market value.