Most people have transferable skills (accountants and engineers being good with numbers; people from the service industry are good with customers or high touch business models; marketing professionals know how to build a crowd). 

{I see that the calculators are still {incorrectly} classifying CapEX as an expense}When modelling a project like this, I tend to be very conservative {upside surprises are more enjoyable than downside ones}.  

I just want to model them and hopeful also build a portfolio in the next few years .

They have both proven the model and the street is rewarding them.

Same builder has bought a new subdivision and is building same model and floorplan of our current home at almost 100k higher price points.

Put your operating strategy into an underwriting model.

The delivery people would need a fob or code to drop off package as long as the door is accessible to the outside

I have a much different viewpoint, which I think is mainly due to a different business model.

Choose the right firm with the right tools and business model. 

That's the usual model for wholesalers.If you actually close on the property, you're free to re-sell - but otherwise, wholesaling as it's commonly practiced is unlicensed real estate brokering.