I am a retired engineer, 37 years with Boeing.

each lot is unique and each city is unique... until you have a house plan.. and an engineered foundation that is approved by the city  and that is put out to bid.. there is no way to know exactly what your build costs would be other than to spit ball .... and really depends on the soil stability to start with

I work a full time engineering job while I try to do all my own repairs/maintenance. 

I went to school for Architecture & Civil Engineering an have been researching real estate investment for over a year.

I don't need nor would I pay that kind of money.Recently one of my engineers creating a site plan for me on a development project had his website redone.

My name is Tyler, I work as an optical engineer in San Diego.

I have a background in engineering and MBA.

Now a professional civil engineer in site development.

If it's you, put some thought in to the types of tenants you'd like to have and almost reverse engineer your strategy from there.

With that info, no formula matters either, as you can reverse engineer the problem based on how much profit you, and the investor, want/expect/need to make.