Not just the scammers, but every day hard use on a tractor is good reason to check it out in person. Some tractors live nice quite lives mowing grass and spending the night in a barn, but allot of them work real hard for years and years. You never know how much preventive maintanence was put into it, nor if everything on it is even working. Some parts are very, very expensive to repair. Hydraulic pumps go out from time to time, and just driving it around a parking lot isn't enough to know this. Never trust the seller, he may be honest, but he also might not consider changing the oil as something important.
I've come across some great deals online, missed out on a few that might have been great deals and walked away from too many that I wasn't comfortable with. Some were obviosly legit, but others were probably fake.
Having a tractor sitting at the freight company and waiting for a buyer sounds like BS. What shipping, or freight company is gonna hold onto something as big as a tractor without being paid to do so? Who would keep there tractor there and not expect it to sell locally?
It's funny that he said he'll accept the money being held in escrow, but I think that if you pursued that route, he'll find some excuse for you to send him some small amount to help cover some bill or expense. Even if he got $100 from you, it wouldn't matter, because he'll disapear and your out anything you sent him.
Don't do it.
Eddie