I performed a heating maintenance on a 2019 gas system. I checked amps, filters, electrical, drains, cleanliness, and safeties. Customer requested I inspect the drain. I flushed the drain with a water/chemical mixture to ensure it was clear and advised that putting bleach/vinegar would help with maintaining the drain. I observed that the emergency drain pan is showing signs of calcium formation on the bottom and that the system does not have a water safety switch. I provided options to the customer for these items. Customer declined during service.