At the end of the day it depends on what your risk appetite is. We've been on quite the bull run so in that regard I would say no, but given rates are super lo

At the end of the day it depends on what your risk appetite is. We've been on quite the bull run so in that regard I would say no, but given rates are super low and mortgage debt is cheap to come by (barely covers inflation), I honestly don't see why you wouldn't investigate it more. If you can make more than the mortgage interest rate, then it was worth it. Using debt is fine is you can stomach a potential drop in a liquid market. That is more psychological than financial, actually. Would you panic sell if your (leveraged) investment drops 30 or 50%? I've come to realise I wouldn't hence I would consider making that investment, but to each their own. This is less risky than using pure margin debt on your investments, because this can't be automatically liquidated.