Uhhh if you have $500k in house equity you can setup a HELOC line of credit in a week. If you want to fully cash out the equity you can do that too.

Liquidating 500k in stocks also takes more than a day to get in the bank.

I was unable to use a HELOC to pay for renovation costs. The banks wanted basically the same assurances as you'd need with a conforming mortgage. I had investment assets several times the loan amount, and a fully paid off house. I ended up having to go private money at a higher cost in order to not liquidate more investments than I wanted to.