What do most banks do when borrowers request to sell real property (our collateral) on contract? Is it allowed and if so, what procedures are in place?

In most real estate secured loans, the mortgage (or deed of trust) is the contract between the lender and borrower. There should be language in the mortgage which will specify what can and cannot be done with the collateral.

Our mortgage states that a contract for deed with intent to transer title at a future date must be approved by the lender in writing prior to. If we find out this has happened without our approval, our mortgage gives us the right to accelerate the loan.

However, I was wondering specifcally about the prior written approval.
- Who and how is this decision made when you have a request?
- What are the banks procedures?
- How much information about the person's buying on contract are we legally allowed to obtain?
- Or should we be looking only at the character and relationship with the borrower?
I REALLY NEED SOME INSIGHT ON THIS! I WOULD REALLY APPRECIATE ANYONE'S THOUGHTS ON THIS. THANK YOU.