@Jeremy Jones, Seems like you got it man!
The county does not check what they documents are or who executed them. There have been cases of hate groups or angry persons forging peoples signatures to record documents to encumber property. Obviously the stuff doesn't stand up, but you still have to go to court and have them issue a judgment to clear your title to the property which can be expensive.
When two parties exchange a property and record a deed with the county, the county is 'posting' it to the public record. You are not notifying the county so much as giving everyone in the wide world who might care to look, notice of what you did. All you have to do to transfer something is make it generally known. Property laws require you do that by giving public notice at the recorder.
There are three ways that I know of why a lender would get notice of a transfer: 1) They review the property records regularly and see that a deed was posted (I think we already understand that this is unlikely since it would be an expensive, time consuming hassle). 2) There notice a different name on the payment check. 3) Insurance beneficiaries change. Lenders required they be name additional insured on an owners insurance policy, If you get insurance put in your name as the buyer, the corresponding change will also be sent to the lender.
Jeremy, Courts want to encourage efficiency in the market by allowing freedom of contract and efficient breach. The Supreme court was clear that its not fraud to violate a due on sale and other lesser courts have said you cant be sued for intentionally trying to conceal a sale because you have no duty to notify them.
To get at @Jon Quigley's question, I usually break down the risk a few ways:
1. Is there a due on sale clause? Read the loan documents and see if it even exists. If it doesn't, no problem carry on.
2. There is a due on sale clause, but I don't care. Why wouldn't I care?
a. The loan was with a huge bank, or service by MERS and sold to a collateralized pool. No one knows where the note is, or who holds it, so none of the 3 ways a lender could recognize the transfer are triggered. The people who would understand who really needs to be paying are so far removed from the people processing the payment, that as long as payment keeps coming in no alarms are raised and no one is the wiser.
b. It doesn't matter to me if they find out because by the time they figure out what happened, send notice of their intent to foreclose, and waited the legally required time before they can foreclose, I've renovated the property or turned around the cash flows and have new financing ready to go, or a buyer lined up. Worst case scenario I can throw the property into bankruptcy the day before the foreclosure, drag my feet filing schedules, and buy myself another month or two to get the property stabilized.
3. There is a due on sale clause, and Im worried that the bank is going to call the loan.
Seller sets up a trust where he is the trustee and beneficiary under the trust. He transfers the property to the trust. This isnt a volition of due on sale because its technically still him as the owner, just though his trust. Now you and the seller do your deal, he quietly transfers beneficial interest in the trust to you as the new owner (this is not a recorded event and the only record of it is the docs between you). Seller stays on as the trustee so that payment and insurance still have his name on them. He gives you all the checkbooks and stuff so there is really no work for him, and any extra work he feels like he would have to do means an increase in purchase price for him. Loan gets paid as normal and no one is the wiser.
The second option is to do some sort of wrap loan where you pay to account servicing, they take whatever portion of the money they need to and then pay it on behalf of the seller to the old first loan. This makes it look like the payment is coming from the same place, but does not overcome the record change and insurance issues.
Im painting with really broad strokes here, but you get the idea. Obviously, if you are going to pull a move with this level of sophistication you need to get a good real estate and tax attorney to make sure everything is kosher for your particular state laws.
In my experience lenders hardly ever notice and wont push the issue until interest rates start going up...people will sell subject to so that the buyer can stay with a low fixed rate when the rate environment is higher. Banks obviously need to move their loans with the interest rates so now they have an incentive to push for DOS.
Hope that helps.