If the owner sells his property, does he have to pay the works decided by the General Assembly?

No, he just must pay for the calls for funds before the sale date. For reference following judgement in the court of appeal: "It is wrong, that the appellants insist that a charge needs to be supported by the one who was owner at the time of the vote at the General Assembly, whilst as correctly stated by the first judge, it suffices to only consider all charges that are due at the time of the sale."

(Trib. Arr. Lux. 24 janvier 1991, 3ème sect, n°29/91 ; Elter et Schockweiler, op. cit., p. 331. ; KRIEGER, G., La copropiété, Portalis, p. 297)