In business, you always need room for error.
A safety zone. A buffer.
If you buy and sell a widget, you want to make sure you don’t pay more than you can sell it for.
The rule of thumb is 30%.
If you think you can on-sell a widget for R100, then never pay more than R70.
That buffer will save you from losing money.
If you buy and sell seven R100 widgets at a 30% margin then you will triple your money.
Give yourself a minimum margin of 30%.