That's a great price!
My advice, buy 2. Run both under load for 30 minutes every year when you change the oil. If you have a space heater, that's perfect to apply a load.
Run all the gas out! I have put those fuel stabilizers in but it's best to just run it all out. Better is to just go with propane or natural gas.
I had something similar and we had of all things an ice storm. Stupid neighbor 2 houses down didn't trim their tree and a branch knocked out their line. 4 houses affected... But because of triage we didnt get power back for 4 days.
I had one of those Chinese generators and it worked good, but they didn't tighten the bolts. They wiggled loose and cracked an engine mount I wedged some wood in and got through the power outage.
I donated it to someone in Grand Isle and bought a new one. I loctited all the bolts on the new one.
Having been through enough damn hurricanes for a lifetime, I made sure it was a "dual fuel" generator. Yeah you get less power out of that 4 kw generator but it will run 24 hours on a tank of propane. And you don't have to wait in line for hours to get propane.
Yeah the gas rotating is the big one, all too many people don't and end up with a rusty tank
Not sure if I've posted it here somewhere, but what I did on my current spare Champion generator is T off the fuel line, and added a second shutoff with a length of hose. This lets me easily drain the tank without having to run 4 gallons of gas through it. Because the tank is not sealed, I make sure to rotate it out every 6 months without fail, and also have Sta-Bil in there. Once 6 months is up, I drain it into a can and throw it in my truck
The oil I don't change unless it hits the OCI actually running, even sitting for 2 years, the oil is fine and never ages out
I try and run it every 3 months under load, in the past I've used a space heater like you suggested, but now I have a few Ecoflow batteries, I just charge one of them up, then I can actually use the power and its not wasted. I always make sure to drain the carb when finished running too, that's also critical
I just made up the maintenance schedule, but so far the generator is perfect. My neighbor has the exact same generator that we bought at the same time, and when he took his out his shed, it wouldn't start and the tank was full of rust!