We need to under what debt stands for before we start discussing it's usability. Debt is a loan you take to help you attend to a need and when is not properly used then it becomes a problem.
For you enter into debt then you must have a means to repay back as agreed and I won't advice anyone to enter into debt all in the name of stating new business as most times it does work as new businesses often have start up challenges the debtor might not have factored into their calculations but if you want to get it to boost existing business that is paying already then is fine
What defines good or bad debt is in usability & ability to repay back and this boils down to individuals. Debt you don't have means of repaying back should not be taken.