Using a HELOC is a very common method to purchase new investment property as it allows you to leverage your current properties and put the money into a new door without using your own cash in the bank. After closing, you could potentially get all of the investment put in by the HELOC back out through a Cash-out Refi, if it was a BRRRR and could pull enough equity. Once your funds are returned you could do the same strategy again provided your DTI can hold up.
There are several benefits that I think make a HELOC a stronger tool for investors than a Cash-out Refi. On the HELOC you will have payments on what you have drawn rather than with the Cash-out you start paying for the full amount of the Cash-out Refi. Another benefit of the HELOC is you can keep using it as long as you continue paying the drawn amount down. A downside with Investment HELOC is the Draw Period is 5 years, at the end of the 5 years I would recommend replacing the old HELOC with a new HELOC that should be at a higher loan amount if you figure in Appreciation and increased equity.
So an Investment Property HELOC is a bit harder to find than the Standard Owner Occupied HELOC. That being said a great option is Quorum FCU. The CLTV on a their Investment HELOC is 80% with a minimum credit score of 680. The will also require reserves for loans of $50,000-$250,000 of 12-18 months.
https://www.quorumfcu.org/lend...
Best of Luck!