Lets say I get started with the process of buying a house. I sign the sales paper and then secure a mortgage. After I sign the sales papers and sign on for a mortgage, but before closing I get a new job. Will I still be able to retain that mortgage I signed for, or will it all go to crap at closing?
I'm in this situation now. My realtor stressed that I should not change jobs until after we closed on the house, specifically because it could affect out ability to get a loan.
The loan (and consequently the mortgage and house) are not in your hands until closing. Wait to change jobs until after you have closed on the house.
There is more risk in changing jobs before closing. That being said, your new job vs. your old job is also a consideration.
If you are staying in the same role (accountant at old job, accountant at new job), with a similar company, making the same or more money, you should be able to re-qualify with your new job.
If you change careers (accountant to house-painter), switch from W-2 to self-employed, change from full time to part time, it is likely to make getting approved very difficult, if not impossible.
I guess it depends on timing. If your mortgage is already approved, there should be no issue. Do you have an obligation / contract to inform the bank about your change? My guess is that doesn't exist.
Banks typically look at your stability as a person. You've been working a number of month / years at your current job. Your new job is 'better' (higher salary). The bank doesn't care.