What if I use debt to invest or to buy assets that increase productivity of my company? Or for some loan you need to pay monthly 5% of your income (for iphone

What if I use debt to invest or to buy assets that increase productivity of my company? Or for some loan you need to pay monthly 5% of your income (for iphone or car), and other loan need you to pay 50% of your income (mortgages). You cannot count them in the same way...