This is essentially borrowing money to invest. It doesn't matter if the investment makes money or loses money the lender will expect payment. This strategy can make a lot of money, but it's also ruined many people. One key thing to watch while implementing this strategy is your debt to assets ratio. Also understand that during a market crash this ratio might change suddenly and dramatically.
I don't make small (sub $10k) purchases on credit, period. Not only is it somewhat risky but it also encourages overspending because it makes the 'pain' of spending money decrease. As for your $2000 mattress, I saved way more money by buying a $600 mattress instead and I sleep like a rock.