Lenders will review your most recent bank statement as part of the pre-approval process. It’s not like they forget about it after that. They’ll take
another look at your assets and bank records a second time during the underwriting process. You’ll need to explain any unusual deposits or withdrawals. Lenders will require clear documentation and a paper trail if you’re putting gift funds toward a down payment or closing costs. Stuffing a wad of undocumented cash into your account is going to raise some red flags.

• Having a late payment hit your credit report before closing can devastate your deal. Payment history comprises about 1/3 of your credit score. One
  solitary 30-day late payment can drop 60-110 points from your credit score. Maybe not a huge deal if you had an 800 score, right? Possibly. But if that 30-day late blemish is a mortgage or rent payment, some lenders will boot your application altogether. Many will require at least 12 consecutive months of on-time payments in order to qualify for a home loan.

• Co-signing a loan is arguably always a bad financial move. But it’s especially risky when you are trying to obtain your own mortgage loan. It
  means you’re financially liable for someone else’s debt. Yes, that someone else might be the most responsible person on the planet. But lenders will still need to factor that new monthly obligation into your overall profile. Adding one more debt to the list could compromise your debt-to-income ratio. 

This probably goes without saying, but losing your job is going to be a big problem. Even job-hopping can present some major hurdles. Lenders want 

to see stable, reliable, long-lasting income. Lenders are likely to slam on the brakes if you take a new job in a different field. OR, if you decide to start your own business. Even if you get a promotion but your income changes to mostly commission-based, this could be a big problem.

Bottom line: Any change to your employment is significant. Keep your loan officer in the loop, and ask questions when in doubt. The last thing you want is to waste time and money going through the contract process if you’re never going to get the loan.