It was a 4 unit when I bought it so I took out a HELOC on a 2 flat I own and used much of that money for my down payment for a conventional 30 year mortgage from US Bank.

Double dipping isn't ideal, but sounds like you might not have much choice.As far as the refi portion, why not get a HELOC instead for that equity?

Used a HELOC on one of my other properties to pay cash for the house and remodel.

And then you have a means of tapping into that value (like with a HELOC or by selling) that will create more cash for investing than you already have to put towards the addition in the first place?

A HELOC is a very valuable tool for any investor.

Is it possible to purchase a home outright for cash, get a HELOC on it to get $ for renovations, then get financing on the property after paying off the HELOC? 

I opened up a HELOC on my primary residence as a safety net.

Used some of our HELOC on our primary residence.

We use a HELOC as our emergency fund if we've spent down our savings to acquire property.

(see the CBO report a few days ago saying TRILLION $$ deficits are here FOREVER) (and the market won't allow that (by 2023) )  THEN I WILL BUY NOTES AND HOUSES HAND-OVER_FIST for 5 to 10 cents on the $ (I've got $112k sitting in my HELOC waiting for this crash) RIGHT NOW, Our LLC is going into F&F's in AL, IN and OH.