Thank you Coral Gundlach, this is great information for any buyer, anywhere!
I personally have had a deal fall through, just once, due to the buyer making purchases and going further into debt. The buyer was deaf and while I did my best to communicate everything to him, I obviously hadn't warned him about making new purchases. I don't know sign language, so our communication was either writing notes to each other or e-mail.
There are many things you should have on your mind. One of the biggest ones is your money. I tell buyer clients, after you are ratified and have loan approval "Do not make any major changes to your financial situation." Can I get a new higher paying job? Well yes, that is allowed. But be prepared to prove it umpteen different ways. The bank is not going to take your word for it. And if you do anything with your money - tell your loan officer about it first, and make sure it's not going to blow your loan.
Don't open new lines of credit. Don't be tempted to get that furniture discount at Macy's. Just wait until after you've closed. The lender will check your credit again, and opening new lines could throw off your ratios.
Don't make a huge payment to anything. Banks want to see cash in the bank. You were approved with a certain snapshot of your cash. If it disappears, they are going to get nervous about your ability to perform at closing.
Certainly don't quit your job or take a lower paying one. They will call employers right before closing to confirm you still work there.
Don't make any major purchases. Now is NOT the time to buy a new car or boat. Wait till after closing.
Sales are falling apart left and right (fortuately, not among my clients) out there due to banks' higher level of scrutiny and tight underwriting. Follow the straight and narrow.