The Rambam writes [Hilchot Gezelah v’Avedah 1:9]:
Anyone who covets a male or female servant, or the house or the goods of his neighbor, or anything that he can buy from him, and he exerts friendly pressure and annoys him until he buys it from him, even for a high price, breaks the prohibition: "You shall not covet" [Ex. 20:14]
(1) What is the Rambam's source?
(2) The Rambam describes pressure amounting to harassment. Is that what is prohibited? What if I told my neighbor just once: "I love your house and would like to buy it for twice its market value"? Is this wrong? Why? He can always say no and that would be the end of it. (The Rambam goes on to describe a slippery slope that may lead to robbery, adultery, murder, etc., but I don't see why it has to be that way.)
(3) Can you tell a poor husband, “Divorce your wife so I can marry her. I'll give you a million dollars and she will live like a queen.” No? Why not? He can always say no and there is nothing illegal there.