@twoinanddone You have to pay the interest on a HELOC during the draw period but there’s no limit on the number of withdrawals. So you can take another advance from the HELOC to cover the interest charge if desired. The draw period can be 5 or 10 years.
The big risk with HELOCs is that as some people found out in 2008-09, the bank has the right to freeze them if circumstances change (e.g. your house price declines or you lose your job). That means you could find the money is no longer accessible at a time when the stock market has melted down and your 401(K) is not worth what it once was. If you can’t afford to pay the interest without further draws then that can be a major problem.