A 1031 exchange is NOT available for owner occupied property so that’s the bad news.The good news is for owner occupied primary residences, for married couples, the first $500,000 of pain is tax free.No need to worry about a 1031, live in the house, sell it, use the $500,000 exclusion and you pay KP tax on whatever profit may exist,2.

And I have to assume the MF are their existing MF that needed cap calls ???

This policy will provide additional coverage above what your existing policy covers.

Demolish The Home and Build New: You can demolish the existing house and build new.

The existing mobile also had utilities hooked up with a $17k impact fee credit that I didn't have to pay to the county.

Hypothetically, you'd need >2K rent on a 250K home to get more than 5% CoC (ballpark numbers with a few assumptions, mgmt fees, putting 30% down, etc), and it seems very unlikely this would exist where I'm looking..

How are you comparing the cost of a new build to one with an existing duplex?

In cities with static or declining populations, the existing housing supply typically meets housing demand.

This ensures that you protect existing tenants from direct competition and support their growth; this will also foster their trust in the ethics in which the property is managed. 

I am a fan of utilizing equity in existing real estate owned to build the rental portfolio though at the beginning, rather than just relying on money saved alone.