A house can't be sold readily. Even if you get in contract ASAP, it's usually 30 days until closing. It's illiquid because 30 days isn't 'readily'. To contrast

A house can't be sold readily. Even if you get in contract ASAP, it's usually 30 days until closing. It's illiquid because 30 days isn't 'readily'. To contrast this with something 'liquid', with a stock you can sell and wire the funds same day if you needed to, 2-3 days if you use ACH instead. HELOC is a loan and doesn't have anything to do with how liquid the asset is.