The best deal you can make is all cash. It means you have to pay the tax pretty quickly, but you avoid so many risks by doing so. The 'discount' is not how to think of the sale, but instead the premium you ask for by taking payments over time.
Let's say you want to sell for $100,000 cash, or you will receive $17,000 a year for 7 years. I would take $100,000 up front, no questions asked.
Let's say you can invest the $100,000 for 4%. If you don't have to touch the money, other than pay the tax, you will earn the 20% difference and have no risk. If the business fails, if the buyer gets ill, if a competitor enters the market and steals clients or market share, you are not affected.
The 20% price adjustment works out to less than 5 years at 4%. That simple math, added to the elimination of so many risks to you actually receiving your sale price, is overwhelming to me. Take the money up front if at all possible.
I can think of a number of deals that fell apart years later, sometimes for risks that weren't either party's fault. The last thing you should want is the legal cost of suing to get your payments from an injured or failing business.
Thanks for asking at Just Answer. Positive feedback is appreciated. I'm PDtax.