Getting a HELOC on a rental home is harder than on a primary. Rates are higher when you find one too.
My first investment property was purchased during a large market dip in 2009. I wanted to purchase additional houses but most of my cash was tied up in this first property. If I just would have either made a minimal down payment or cash out refinance i could have continously purchased additional houses and could easily be retired now off them. (Opportunity cost).
when i was finally in a position to purchase more houses the prices were substantially higher. I followed a BRRRR method. Originally pay cash, then refinancing after renovating. This way I have the cash again to purchase another property. Unfortunately with today's high rates and prices my opportunity to find very good deals has passed for now. If I only had more available cash when prices were low i could have cleaned up.
No matter what you need to make sure you are not over leveraged. I have always been very conservative on this.