There's a right way and a wrong way to go about buying a home and you have touched on what I consider THE most important first step one can take towards accomplishing the goal of home ownership - vetting your financing capability.
Please review the following to understand what constitutes a true Pre-Approval and why it can save you from wasting about $1,000 on a cancelled transaction: http://www.Steven-Anthony.com/GettingStarted
Your Pre-Approval is only as good as the level of underwriting diligence expended by the person you work with. The Mortgage Brokers/Bankers I work with understand when I refer my Clients we want to identify any issues that might qualify as a â€œred flagâ€ or Pre-Approval caveat. Many times, even before going into contract, the underwriting department is brought into â€œthe Pre-Approval loop" for guidance, if necessary. You should demand the same from anyone you work with.
If you are not sure where to obtain your Pre-Approval you can ask any of the RealtorsÂ® on this forum who they would recommend in your area. If you are not happy with a referral I would suggest you work with a Certified Mortgage Planning Specialist. Mortgage Broker/Bankers with this designation have been trained in financing, investment, and tax planning topics: http://www.cmpsinstitute.org/public/menu
Having been both a Mortgage Broker/Banker I have an experience-based opinion on where you should be seeking your financing and Pre-Approval:
"Retail Banks vs. Mortgage Broker/Bankers"
(Includes useful links to "Rate Shopping - Do It Right" and "How Mortgage Rates Are Determined"