First, welcome to the forum and to the community!
I been thinking of this for awhile, I came up with these ideas recently.
My thoughts are to always have (or access to ) WD40, tools, a pickup truck/van or flat bed handy and maybe a sawzall or a cutoff wheel ($20 at Harbor Freight) and a small generator and a couple of 5, 10 and $20 dollar bills handy. If you see a dish not being used, contact the owner and ask if you can have it. If they are reluctant, offer them a 5 or a 10 dollar bill.
If you see a work crew dismantling a building with dishes on top, a couple of $20 dollar bills on hand might be the order of the day. Remember the people taking the building down are on a time frame and a little "green" can go a long way.
Most importantly, what is the dish worth to you? Take E-Bay for example...you can find "World Direct" oval dishes for $65 to $80 shipped. If you see a Prime Star dish with arm and LNB, if you can get one for free or even $20 or $30..you are still ahead of the game.
Even if the dish has no LNB or arm, a Primestar dish might be worth $5 to $10, others here have bought dishes minus the arms and fabricated the arms themselves.
C-Band, ...like others have posted...some people just want it "out of there" and be willing to give it away for free. If the dish is located in the middle of the yard and you don't have any help, a hand truck, small generator and a sawzall or decent cut off wheel can cut the pipe off, and you might be able to dismantle the dish right there and haul it off in small pieces with the help of a small hand truck.
If the C-band dish is in pristine condition, the LNB is good, motor/acutator works and the owner is willing to throw in the analog receiver ..it might be worth it to spend $25 to $50 or more. Though the analog receiver might be out dated, you can use it as a "dish mover".
I spotted a Primestar dish minus the arm near Central KY and when I get down that way again, I'll try to find the owner and ask if I can have it and or offer them a 5 or a 10.