Multifamily -Ground up -Houston - Need to verify my numbers

[Jiji John]

We are (3 partners one partner is an Architect) planning on a multifamily project and identified the lot, talked to city its commercial zoned and no restrictions. What i was proposing is to do it in phases and build two duplexes (4 units ) on one side and sell it then finish off with construction loan or lease and refinance. As per my numbers its not feasible right now to lease out but eventually we might get better numbers , so leasing may not be our option.

This land is 17000 sq ft and like a triangle also needs some serious prepping to utilize the lot fully. A major portion was eroded into the water way which is passing thru the corner and we may need a retention wall, approximately 150 feet.

Phase 2 is also another 2 duplexes and each unit in all phases will be 1800 sq ft. Please go thru my numbers and  i need help from expert opinion.

I am missing lot of numbers in the whole transaction which i am not in a position to calculate now. I may have some whole stupid numbers and assumptions, let me know whatever it is. 

Thank you