I agree with Malaga's advice. The last place I purchased I made an unconditional offer which was only valid for 24 hours.
When I'm in the market and looking to buy I always have very little "chat" with the agents. I always find they ask the same questions, where do you live? What is your occupation? What other properties do you own? How much are you financing and with what lender?
I know they are making inquiries for to see how wealthy you are. They want to squeeze every drop of juice from the orange, I have no problem with them doing this because I except them to do the same if they were selling for me.
As per Malaga's example above putting a pre approval letter is showing your hand to the agent is just stupid, of course they will come back for more gorillas. They must have really wanted the house.
