It is cheaper with better financing to purchase a property with an existing ADU than add one.  

Given the general importance placed on cash flow, is my line of thinking incorrect and therefore should buy something cheaper or look more into duplex etc?

Flipping properties creates taxable events.

The increased depreciation deductions can offset your taxable income, including gains from the sale of the previous property.

Not only does this lower your taxable income, but it also allows you to support a cause you’re passionate about.

I find if I do the "heavy lifting" like drawing out a system and or the floor plan of the cabin, you can find a guy to do the "official" work fast and for a cheaper price than if you sit back and do nothing.

Plus you get interest income on top of your principal payments, too.Also allows you to spread the taxable gain out over time, which would help you keep taxable income low and potentially still contribute to Roth IRA in the year that you sell. 

I'll talk about this next.2) Deal structure: Currently, the types of deals that have experienced huge distress or imploded , have generally been the ones that were very aggressively structured.Floating rate debt is cheaper, but come with the risk that interest rates rise.

Could I have learned what I learned during that 1-year program for a lot cheaper by reading books and articles.

The IRS partially validated it by saying it is taxable, but they also tax illegal earnings.