There are a few consignment lots. In Idaho it is illegal to park a rig on the side of the road with a "for sale " sign on it, unless it is parked in front of your house (and even at that state law says it must be be moved within 48 hours), a friend's house (as long as you are at the friend's house at the same time!) , while shopping, etc.
The state takes a dim view on turning the sides of its roads into used car lots.
It can be parked on someone else's private property, as long as you AND the property owner have a signed agreement.
I know the valley L.E. agencies have been tuning people up about this lately. Meridian and Boise had a real bad problem on Eagle Road, which I trhink has been dealt with.
Our agency will call the owner, advise them of the law, and get it moved, usually within hours, or by the end of the day. If they become "difficult".........we tag it and then tow it, at the owners expense.