you have to buy the estate deed of the shop.
only those estate deeds that are in player's possession can be traded now.
in the beginning such estate deeds came with a rental fee, which had to be paid to MA (you had to pay rent for your "own" property!).
in reaction so many real estates got abandoned (and therefore unaccessible), because ppl didnt want to pay the high rental fee.
this gave such a desolate picture of the economic system of the game, that MA had to give up on the rental fee.
alot of shop estates and other real estates are still in MA's possession ("Marcus Callendar Estatebroker"), but they never sold.
And seemingly MA will hold them for the second tsunami-like wave of new players, which they expect to come soon™, when they fixed the bugs...