Without wasting much of our time deliberating on the matter I think it will take someone who is into real estate business to be able to give us a good explanation concerning this matter.
From my personal knowledge, selling a building after the construction gives more profit than renting it annually because it will take longer years to be able to make the capital used in the building project before the profit making while if the building is sold after the construction, the profit made can be used to start another project that will be ready for sales even before the proposed building for rent profit can be generated.
Not everyone is ready to wait for years to take profit of their rent it only takes someone who's interested in taking future profits to endure for years to make profit of his building project.