If not, do you think it's fair that he donate his time/effort to you for nothing in return?

He lost me there too.If the seller remains owner, while the buyer is supposed to be making payments towards buying, then the buyer isn't buying the property...they're making donations to the seller.

Instead of trashing it, donate some of the materials and recognize the write-off to charity at fair market value

Last year I had a client wait until October to tell me he donated a piece of land to a church the year before and didn't get an appraisal on it....

I really think if you can get people to make big donations to your city council/local politicians then you will have a better chance of  accomplishing your goal. 

., REO's from banks, tax sales, unwanted parcels that were donated to non-profits, like Habitat for Humanity, ------> "you name it, and I've tried it!

They settle for ho-hum deals that only cash flow because they plan to donate 100 hours of work every year on each house. 

If you need cash for it, YOU ask the city, or have the volunteers set out change donation boxes in every business in town--7-11, hair shops, Walmart, etc...Also big companies like Walmart might make donations if YOU contact them.In a nutshell, I'm saying a BIG Project needs a full time Vision Person to Steer it and spur it on when it stalls (which it will from time to time).

Well - I emailed a couple of notices letting her know that the lease was up, and stated no holdover, and that any items left behind will be considered abandoned and donated or thrown out. 

Donate it for a tax write off   ( probably not a feasible idea but I have donated many houses that i knew were losers and took the write off).