Please make sure you have an agent representing you or at minimum have an attorney review your contract as to cover these most basic principals in purchasing a home.
Buyers normally pay for this service, and the report is yours to keep. Cost depends on the square feet of the home to be inspected. A typical inspection for a 1700 s.f. home will cost $350-375 depending on the Inspector you choose to use. You may find it less expensive if you do a search by the Yellow pages or the internet. You may want to consider hiring a local experienced Realtor to be your Buyer's Agent exclusively.
You want the home inspector to be working for you. I personally wouldn't want the seller to hire a home inspector for me. It's kind of a conflict of interest situation for me.
Like Ute said, I also recommend that my sellers get a home inspection prior to listing the house. Once they have a 3rd party (home inspector) tell them the negative parts of their house, they are less likely to over price their home. However, I still recommend the buyer make their own inspection as well so that they feel good about the home.
In Tennessee, if a house has structural problems and/or subfloor problems, floor joist problems, the home inspector will recommend you hire a structural engineer to take a look at the problem. A home inspector can't give advice on things that are out of his scope...and generally, subfloors and structural issues that MAY be causing the floor dips may be out of his scope and he would have to refer you to a structural engineer. If you suspect the damage is something like that, you may want to go ahead and hire a structural engineer that also does home insepctions...it may be a bit more costly, but would save you from having to pay twice. If you're working with a buyer's agent (and I hope you are because your agent will be able to negotiate for repairs if they are needed), ask for SEVERAL recommendations and call them yourself. Let us know what happens.
I usually suggest to my sellers that they consider getting a prelisting home inspection as it will put the cards on the table for prospective buyers and it will also give the seller an opportunity to determine the true condition of the property which helps them price the property right. In my experience, buyers feel more confident making an offer when they can see the inspection report prior to making an offer and the chances of the escrow falling out because of something that is discovered during the inspection period is drastically reduced.
Please note that home inspectors will only inspect what they can see. They will not lift the laminate floor to see why there are dips. They will crawl under the house and look at the underflooring to the extent that their view is not blocked by insulation. If they can't see what they need to see to make a determination, they'll note what they observed and that they were unable to access the area due to insulation and they'll recommend further inspection (e.g., the home owner could remove the insulation to make the subflooring accessible to the inspector). I usually state in my offers that the seller agrees to provide access to all areas and remove obstructions to allow full inspection. If the inspector comes and can't inspect the garage because the seller has boxes stacked up to the ceiling, it would be the seller's responsibility to remove those boxes and pay for a re-inspect. Seems only fair to me, but unless it's part of the contract, disputes can arise about who is supposed to pay for the re-inspect. Since time is of the essence in real estate transactions and the buyers only have a limited time to complete inspections, it's important to make sure the inspector can do a good job the first time around.