To defer all taxes with a 1031, you'll have to reinvest all of your profit, which looks to be more than 10% of the purchase price.For the residential property, you say Annual Rent/unit is $46,800, which is $3900/unit/month.

For example, according to this link, HVAC systems suffering from deferred maintenance can expire in 15-18 years.  

If held over a year, it is normally taxed 15-24%.You might qualify for an exclusion as a a small business stock - something to look into, preferably with a tax pro.You can also roll the capital gains into an OZF and defer the capital gain plus get tax=free growth under the right circumstances.

Not to mention that appreciation can potentially be tax deferred if you exchange into another property later on

Alternatively, in another scenario, I've thought of executing a deferred exchange by acquiring 100% of the vacant land with a portion of the relinquished property funds held at the intermediary where the EAT holds title to property, then initiating the construction by also funding an improvement exchange on that land with the remaining balance of the relinquished property funds held at the intermediary. 

Claims best asset protection and deferred income and cap gain tax, with his titanium irrevocable trust.

This is precisely how real wealth is made - tax deferred appreciation. 

And when you use the correct process you get to defer indefinitely any tax you would have paid on the sale of the old property including any depreciation you would have had to recapture.If you just sell that duplex you will pay tax on the profit plus depreciation recapture - even if it is part of the divorce settlement.But using the 1031 exchange you and your ex husband should be able to sell the duplex and purchase other investment real estate (separate properties for you and he) and avoid all tax.I'll pm you with some resources.

Property is in rough shape with a lot of deferred maintenance.

The older homes have been a major time suck as there was major deferred maintenance in almost all of them.