In a dilemma! to build or to sell a vacant lot?

[Nkechi Jarvis]

I have a vacant lot (40 feet by 108 feet) near University of Houston, Texas Southern University,  and Downtown Houston; and I have just recently re-platted the lot as two separate lots (each is 2,160 sq. ft. UNIT A & UNIT B) to build a duplex. My initial intension for re-platting a lot of this size was to be able to sell one unit if the need arose or to rent out the units as fully furnished mid term rentals, including utilities. I am concerned about the cost of building materials.  Initially, I thought of building a three story duplex but found out that the cost would make return on investment very challenging. Any suggestions about floor plans on small lots for two story duplex?