The golden rule is "don't buy bank product (mutual funds /other investments) buy the bank (bank stock)It shouldn't be an issue. I carried a perpetual balance on my HELOC for well over half a decade while trying to crawl out of a badly leveraged investment after the DotCom bust.
Also the banks push loans for investment all the time. Of course, the investments they are pushing are the bank's own mutual funds.
High MER on the fund + collecting interest on the loan - win win for them, they are eating the customer's sub sandwich from both ends...
Why pay them MERs when they will pay you with dividends?