Trevor is right and wrong. Two years consistent empolyment especially with constant increases should be absolutely no problem. However, a pre approval is based on actual documentation, such as credit reports, tax returns, pay stubs, bank statements and documented proof of where the doownpayment is coming from also if out side help is needed such as a co signer is needed and their documentation, whereas pre qualifications are usually based on conversations and as such are worthless. I have every buyer I work with pre-approved before I will work with them because to do anything else is a complete waste of time forthem as well as myself.
When you find the correct property you want your offer to be seriously considered, especially if you are in competition with another buyer. A proper pre approval insures that a strong case can be made on your behalf.