There are a few people I refuse to sell fish to. Guess you are on my no fish list.
I wouldn’t buy fish from anybody that would say fish don’t age. Because you’re ether a liar or desperately confused. Tell you what, take one of your mollies, put in a separate aquarium, keep it well fed and clean and uncontaminated by other fish and tell me in 5 years if it’s still alive. It won’t be, and it will have died of old age. Because fish age.