The rental sanders are faster and less back breaking!

If they do come back and start throwing their weight around then you get out your check book and let them fill in the blank to get them to go away.

Will make your deal cash flow faster, yes you will be giving up cash flow for greater security and safety. 

There is no deviation.  5+ units are appraised using the income approach with some weight given to the sales approach.Your numbers are too tight using the sales approach for this property. 

Your duplex will appraise the same as any other stick built duplex, it'll insure the same, etc. it is NOT a mobile/manufactured home, but you're going to have your construction loan for a lot shorter period of time which means less interest you pay and the faster you get in a tenant and start that cash flow.Importantly.. you should come in WAY below a $250 sqft price.. here in Houston I have a modular builder that starts at $88 sqft and with the improvements i am requesting just about hits $100.

A gap was left that allowed the weight of the street traffic to eventually break the pipe right at the 90 degree angle, which allowed it to fill with gravel.

They Appreciate way faster than a mobile home.  

Its just a faster path in my opinion.  

From my pov, I suggest to prepare now to know a) what well-cash flowing and appreciating/depreciating property looks like to you so that you can cut losses early and b) how to screen for and handle employees, as the advantageous position that you have might risk draining you of your time if you accumulate property way faster than you delegate tasks.

Property managers — specifically good ones — are worth their weight in gold.