As long as you can borrow below 6%, you should be trying to lock in as much debt as possible.

@Reagen Natho Why would it be 1k to change locks ? 

Disclaimer: I've done this exactly once.Here are some things I did in the last few days of renting out my single-family house.Go around to all the rooms and make sure everything works - doors open and shut, windows open, shut, and lock, mini-blinds (if any) are securely mounted and work, curtain rods (if any) are securely mounted, closet rods are securely installed, none of the light bulbs are burned out, etc. 

So I have $20,000 in the bank locked in a GIS account for one year.

@Derrick Locke I have a list of lenders that I use.

I still have all of the aforementioned benefits because historically rent prices will not decrease AND I am still locked into the loan based upon the current market value which made sense in regards to cash flow.

I was planning to refinance into another conventional mortgage from my current duplex to lock into the low rates, and also pull cash out to pay off the rehab that I did in the duplex. 

You should change the locks.

The L2O will lock me in though, wont it?

There's no one right answer to this, but if I were in your shoes I'd probably put a conventional mortgage on it now to lock in long-term financing at historically low rates, and use the cash to purchase more.Nothing wrong with a HELOC, but it will be at a lower loan-to-value ratio.