HVAC stuff is modular and easy to fix yourself provided you don’t need to open the refrigerant lines. Start capacitors, run capacitors, and contactors are all items that will fail (especially the outdoor unit) and cost under $7 each. The HVAC repairman will charge you $70 each for those parts, and $400 for a few minutes installation. Open yours up and just buy them now so when they fail (always middle of summer heat) you can just put new ones in immediately.
Even blowers and fans are inexpensive ($150) to do it yourself.
Now messing with refrigerants or natural gas; call someone.
The water heater has an aluminum or magnesium anode rod to prevent corrosion. That will dissolve after several years. They sell them at the big box hardware store; they screw right in.
I've repaired natural gas appliances several times. Usually it is some sort of flame sensor and rather easy to replace.
"The flame sensor is a rather simple device located at the burner assembly. It's not much more than a thin, usually bent, metallic rod that sits in front of the flame stream inside the furnace. The purpose of the flame sensor is to confirm to the system that whenever the gas valve is open, a fire is actually present"
Good to know. I was thinking more of the plumbing. Specifically the equipment needed for refrigeration. I’d do flex connections for natural gas, but not the black iron gas lines.
Even blowers and fans are inexpensive ($150) to do it yourself.
Now messing with refrigerants or natural gas; call someone.
The water heater has an aluminum or magnesium anode rod to prevent corrosion. That will dissolve after several years. They sell them at the big box hardware store; they screw right in.