Can a HELOC be used on a future primary home as a down payment?

[Chance Love]

I've lived in my primary home for 10+ years that has a great amount of equity and I'm considering doing a HELOC and turning my current primary home into a rental which will produce great monthly cash flow based on the current market. My goal is to pull 20% for my next home from my current primary since I'd like to downsize and use that towards my future primary residence as a down payment. Is a HELOC typically accepted or not as a down payment for a primary home or is it case by case? Thanks in advance!