I just had a very similiar conversation with a referral from a realtor. Here is what I got back from an underwriter with one of my investors.
Projected or proposed income may not be used as part of qualification income, unless the borrower will be employed prior to the loan closing and all of the following requirements are met:
â€¢ A legally binding employee contract must be provided. Offer letters are not acceptable.
â€¢ The borrower must have started employment at the new position as per the terms of the employee contract.
â€¢ A Verification of Employment (VOE) is required to verify the borrower has started the employment prior to closing.
â€¢ Paystub from new Employer
These will be requirements for the loan to get approved, you can apply now but make sure your income on you application will line up with actual earnings.
In reguard to FHA expenses increasing, it is true, but it isnt that big of an issue in the short term. It will start going into effect April 1, 2013. I have a blog post about it here
Congratulations on the new job!