Development Opportunity or fantasy?

[Wilson Zu]

Hello everyone.

I am here daydreaming during my 9-5 day job but contemplating in taking a development project of a lifetime.
Putting my thoughts and numbers here and hope you guys would give me a sanity check.

My background in RE: Have about 10 years of experience as landlord for a few rentals as side hustle.

The project I am envisioning is the development of approx. a dozen of townhomes in a fairly desirable side of Atlanta, GA (e.g. Sandy Springs).
The ballpark numbers
Land = 1mm.. previously approved for 12 townhomes
Constructions = 2.5mm.. Using estimates of approx. 1mm per building of 5 units. ~1800 sqft each
Land + construction = 3.5mm
ARV = 4.56mm..  ~380k per unit X 12
I am sure there will be other costs associated with financing, sales commissions, marketing, overhead, etc.

Have anybody done this type of development? What are your thoughts? How did you learn to take such challenge?