I am thinking of buying a home which has a third bedroom, which I would like to turn into a den. What would be the cost of removing a wall and a closet? No matter how easy this may be, I am unable to do the work myself

Not knowing what plumbing, ventilation or electrical may be in that wall you best bet is to get 3 contractors to give you a bid.

Before you do this make sure that wall isn't a bearing wall. That can be check out from the attic or simply by the roof design and truss bearing plates.

If all OK and you are committed to this you can poke some holes in the wall between the studs to actually check for mechanicals. Look for ( outlets/ phone jacks/ cable TV / heat AC vents/. Bathroom venting stacks/drainage/ radon pipe/ etc.

This will help greatly to keep the " extras" out the project bids. That alone can ruin a working relationships between customer and contractor.

To be honest as Contractors we need to plug in a percentage for the unknown. Or put a " clause" in the contract or both. So the more that's seen the more accurate the bids.

As bal1 mentioned get 3 bids and don't forget References. I offer a certification of Job insurance to the customer to let them know things are on the up and up.

My City requires job insurance cert to be on record for my city contractors licenses to be issued and for me to pull a permit. But not the townships yet.