In principle, it is permissible to sell as well as to buy plots of land that are developed or undeveloped. The same is with buying shares.
Dr. Monzer Kahf, a prominent economist and counsellor, states the following: it is permissible to sell/buy plots of land that are not yet fully developed as long as the appropriate authority designated their development plans and the plots become recognizable (i.e., they can be defined and land-marked by a specialist). It is also permissible to buy a share (certain percentage) of a land that is not yet designated whereby the plots are not recognizable.