Negotiating to haul away somebody else's scrap

As my username implies, I'm an excavator. I've handled a lot of scrap over the years, but mostly stuff I've dug up, or retrieved from the dumpsters on jobsites we've worked on. A different opportunity presented itself today, and I'm not sure how to approach it. I know some of you have done things like cleaning up a farmer's accumulation of used up equipment and scrap, and had some sort of a deal worked out with the owner. This would be similar.

We looked at a demolition job today, for a client we already do business with. There are several buildings, full of...stuff. Also, scattered across the site are some used up cars, trucks, and construction equipment. The current owner is supposed to clean up the site, and empty the buildings before the sale to our client. Some of the stuff might be saleable as-is. Some of it might have "more than scrap value", and some of it might have fit one of those two classifications 20 years ago, but is too far gone today to be anything other than scrap. No matter which, there's going to be a lot of effort involved in getting it gone. We haven't met the owner, and don't know whether he'd even be interested in having help, or if he's willing and able to handle it all himself.

This is all very preliminary, but the time and equipment is available right now. We're liable to be too busy in a couple of months.

The best case scenario would probably be he says, "haul it all away and keep whatever you can get for it", but I doubt that'll happen. At the other end of that spectrum would be that he wants an exorbitant amount of money for it, more than it's worth. (Assuming he's not planning to do all the work himself anyway.)

So, what's a good place, and a sound strategy, to begin negotiating to make it worth our while?

Thanks in advance for sharing your wisdom.