If you're planning on managing the rental unit yourself, you'll learn a lot about owning rentals pretty quickly.

The 2-3% points in extra cost are worth it if you plan on using as I described above because the use would be for a few  months at most and due to that short term use you can survive a rate adjustment up.But, if you have no plan to payoff the debt like when using for a down payment on a long term hold why pay the extra cost for flexibility and have the additional risk of the adjustable rate with the amortization looming when you can get a fixed rate second mortgage. 

I have learned to color code (highlighter) and plan the month/year or week ahead. 

Unless you are buying at a significant discount, or are hacking it, or have some other value added strategy or plan.

If that is your plan then go do something else.

This strategy balances tax efficiency with proper estate planning.

We are building a place with HELOCs then after it is built we will finance it and pay off our HELOC, at least thats our plan. 

What did they say is the plan?

Now, are you planning to house-hack and live in one unit, or going full rental?

I'd like to accumulate enough properties to cash flow 6 figures, which would likely be a 20 year plan.