Surely you're not suggesting leveraging your home against a luxury purchase? If you lose a job or suddenly incur tremendous medical bills (more of an issue here than across the border, perhaps), not only do you have to worry about your mortgage, you now have a HELOC over your head.
My fault. I Should have been more explicit. The assumption is that you have A) the cash available to purchase B) an adequate emergency fund C) a diversified portfolio of investments D) Enough equity in your home where a refinance would be allowed (not sure what this is like in the US. Here in Canada you can only refinance up to 80% loan:equity on a fixed term mortgage, or 65% on a HELOC). If you literally don't have access to the capital required to purchase, then no, you should not be buying either way.
If your paying cash, your just leveraging your investments (long term goals) against a luxury purchase.
If "life happens" I'd rather sell my timeshare for what I can get not having to worry about if I can sell enough to pay off my HELOC.
And rewind to December 2007. Knowing what you know today, would you be dispensing the advice that it's better to take out a 2.5% loan against your home, given how you can invest in the markets and make better money than cash, to go see a fake castle year over year? A lot of people thought exactly this back then.... then life happened.
This all depends on what stage of life you are in. If you are closing in on, or in retirement, then your expected rate of return should not be enough above that 2.5% where the risk is worth the reward.
However, if you are on the younger side of things and are still 10+ years away from retirement, you have plenty of time to ride out the downturn of your investments. Your long term average expected rate of return should be much higher than 2.5%
At the end of the day, if 2007/2008 happens again, you can still sell your
DVC for whatever you can get for it. You also should have an emergency fund, and enough equity in your home that should leave you far from being underwater.