Above of some of the reasons I recommend that people not get a Line of Credit. They're actually only Lines of CREDIT until you actually use them, then they are instantly Lines of DEBT. The banks purposely misnamed them because Line of Credit sounds great, but who would want a Line of Debt ??
One of the reasons they're increasing the rate is that they're trying to encourage people to pay them down/off. Lines of credit cause banks to have a lot of credit "exposure". If they approve you for $100,000 LOC but you only use $20,000, the bank still has to keep reserves to back up the $80,000 that not earning interest for them. Multiply that by thousands of customers and the bank has hundreds of millions of dollars they can't lend out to actually earn interest. (gotta look after the shareholders)
Not only can they change the rate at any time on short notice, they can also call for full repayment if THEY feel you're not managing your credit well enough.
My rule is that credit line limits should only be for an amount that can be paid off, in full, in a year or less. Otherwise - get a regular mortgage. (a mortgage is simply security for a loan) With Fixed mortgage rates being in the 2% range, borrowers are far better off borrowing what they think they'll need as a regular mortgage. If someone has extra money from the mortgage, it can easily be invested somewhere else an earn more than the 2% cost, and even put in an RRSP that also generates an income tax refund.