How many Due on Sale clauses have you actually seen enforced?

I do generally agree with the sentiment of Austin and the other hosts that fundamentals will always win out in the long run, and this by nature is a long term industry, even the sales side I'm learning.  

Is there any creative way to avoid/reduce capital gains tax on the sale ?

It should include details like the purchase price, property description, and terms of sale.

Usually a post like this or even remotely similar to this is posted by a newbie or someone that has a coaching program for sale. 

This defers capital gains and depreciation recapture taxes on the sale of your fourplex.After converting it into your primary residence, you may qualify for the primary residence capital gains exclusion ($250K single/$500K married), but only for appreciation after the conversion; gains from the rental period remain taxable.

I've been toying with the idea of adding an ISA to my sales business.

You're supposed to have a license in every state if you are representing either a buyer or a seller in a real estate transaction, or acting as an intermediary in the sale of real estate.

There are several duplexes out there for sale and if you do it right, it can be financially beneficial for you.  

But if it’s a sale, some buyers might be okay with a few unfinished details, especially if you disclose them upfront.