That said, the slimyness of many lending institutions, which includes a great many more than mere banks, is remarkable. From the heavy handedness of upselling people on the size of the mortgage, to nasty clauses hidden in contracts (pre-payment penalties, etc). Verbally quoting one rate while writing on the contract another. Suggesting people falsify incomes and not bothering to check employment. Etc, etc, etc.
Any time you have a commissioned salesman doing mortgages, you will have commission enhancing sales being pushed and made. It is no different that car sales.
You are sooo out of date it's not even funny. Back to those qualifying standards of Fannie & Freddie (the good guys in the mortgage industry) I mentioned earlier, the standards are set so that there aren't any of those hidden nasty clauses. Haven't been prepayment penalties on a conforming loan, VA or FHA for literally decades. The documentation is standard so that it doesn't vary by where you get a loan or usually even loan type. The Fannie & Freddie qualifying standards and loan paperwork is so good that it is the gold standard world wide.
These standards go into so many areas you aren't aware of - It even goes into how your house must be built. Between FHA and Fannie you can thank them for an energy efficient home. You also must thank them for a home that is designed to last longer than your loan. Without FHA you wouldn't even have sheetrock inside your house as standard equipment or insulation. You may think of FHA standard carpet as super cheap, but do you know that when that standard was enacted it was thought of as exorbitant and outrageously expensive.
Fannie and Freddie were designed to be fair for all parties and to keep either party from being taken advantage of. Those mean ol' unscrupulous banks (think Jimmie Stewart in It's a Wonderful Life" can't even force you out and sell your house for an insane profit. The money doesn't belong to them, it belongs to the borrower.
As far as quoting one rate and writing up another? Hmm, the only thing I can come up with is when someone calls in for a rate one week and writes a contract another (even another day or later in the day sometimes) because rates change as the market changes. You can count on a rate change every day (usually by just a little), and as a lender finds out more about a person they may find out that person doesn't qualify for the A++++ loan the caller said they did. "I gots me good credit" usually translates into I eventually pay my collections off if they won't leave me alone or I think I want to buy a car or a house. (BTW NEVER pay your collections off anymore, the credit laws have changed and that is guaranteed to lower your scores)
And if you are talking about quoting one rate and writing another on a contract then you are talking about Realtors not Lenders because Lenders have nothing to do with the writing of the contract. But most contracts state that your rate not exceed a certain percentage so good Realtors would give you a little pad so that a Seller couldn't arbitrarily cancel your contract if they decided they didn't want to sell or had a better offer. The rate put on a contract has nothing to do with what interest rate you receive, but your credit, income, outgo, assets, etc. do.
There is no incentive for a lender to screw the borrower as there is so much more money to be made on referrals of their friends, family and co workers. Commissions keep your loan costs down. Banks with fixed overheads have typically more expensive loan products than do commissioned Brokers. As a matter of fact studies credit brokers with driving consumer mortgage rates down by over 1/2% below what banks would have had on their own. I do both Banker loans and Broker loans and I can always be about 1/4% lower on the Broker side.
You go to jail for falsifying incomes or anything. It is investigated by the FBI. They used to randomly check about 1 out of 20 transactions unless there were other red flags. One red flag is a plethora of certain loan types or documentations by a lender. If that happens 100% of that lender's products will be investigated. It ain't worth it! Loans are Federal instruments which mean offenses are Federal offenses and you go to places like Alcatraz or Sing Sing. The Big house seee! (doing my best Jimmie Cagney imitation)
As far as not checking employment, etc. After Mr. Clinton, the Gramm/Leach/Bliley act & the Community Reinvestment Act Lenders were prohibited by law from checking if a borrower didn't want you to. We would have been discriminating and would go to jail ourselves if we took it upon ourselves UNLESS there was clear cut evidence of fraud. What could possibly be fraudulent about doing a stated income loan for a salaried person? I mean after all if they actually made the money they claimed then we could get income verifications or paystubs - oh wait, we weren't allowed to or we'd go to jail! That means there was legal fraud. Don't blame your lenders, blame your legislators.
B loans were another story altogether. B loan wholesalers encouraged lenders not to document the loan 1) to make it easier on the lenders 2) so the B lender could charge higher rates. The higher the risk the higher the rate.
Oh, and ALL qualifications are based upon house payment, not $xxx,xxx of loan. It's a process to convert $ to loan amount that many lenders will do to help a buyer because unless you know what size house $X of monthly payment corresponds to how could you go house shopping?