I think the sentence should be:
"If business is good, it pays to advertise. If business is bad, you've got to advertise."
If business is going well, then it is advantageous to maintain your profile and prominence through advertising - 'keep your name on people's lips'. If business is poor, then you'd better start getting some customers fast, and you do this by advertising your products/services, reaching out and making people aware of your business and what it offers.
- For Teachers