Basically thats a majoy stuff up. Ur correct about the caveat, he cant sell or refinance until it is removed. and anyone can put a caveat on anyone elses property. As far as them building a wall on ur property, thats a huge f**k up by a few people. Council mainly, cos u cant generally build within 50cm of ur property boarder. depends on ur shire of course. It happens with fences all the time, but they are easily moved.. a Wall of a building however.. oops! call ya lawyer mate!