Couldn't find the ad., but I'd suggest they're largely a waste of time.
I repainted a Bateman crop sprayer for a local arable farmer,contractor and haulier.
His wife approached me knowing I shot with air rifles and asked if I'd be willing to take care of feral pigeons on the yard.
I agreed,as time went on they rang several times to remind me of my duties and offer permission to shoot elsewhere on their land.