Home equity loans are predominantly used by middle income households [0].
The rich can borrow against securities at the call money rate, currently 2% [1]. Much cheaper than borrowing against real estate [2]. The less rich swap it to a fixed rate for added security; the richer take the rate risk. (They likely have natural hedges.) The super rich seek to borrow at or close to the SOFR [3], typically having Treasuries or similar structured products for the purpose. (If they have a business with float, that could be even cheaper than SOFR.)