I looked at a home last night and I have concerns about the floor. The house does not have a basement. It has a crawl space. In the kitchen there is laminate tiles. In certain spots, the floor dips. If you bounce on that spot, the floor moved. The rest of the house over the crawlspace had laminate floors and I did not notice any dips. Perhaps the floors hide it. I felt one spot in the master bedroom dipping as well.
What could be the problem? Is it expensive to fix?
(I noticed in the crawlspace that a fan was down there to keep humidity out).

If you're serious about this house, surely you will have an inspector look at it. There is not enough information to be able to suggest a cause of the problems, but there are many crawl spaces in the world, unfortunately, that have not been properly done.

There could be rotted lumber down there, there could be a cracked floor joist, the floor joists may be inadequate for the span, the subfloor could be either rotted or inadequate...there's no way to know without looking.

Ask the inspector to check and see if there is a vapor retarder visible, and if so, is it taped to all walls and floor penetrations,, with all joints taped. Ask him to check on the adequacy of the crawl space vents, and to ensure that they are open. Ask him to check for any signs of water in the crawl space.

Thanks for the good advice.
We will be getting an inspector if we decide to make a bid.