There are enzyme based fuel stabilizers that can keep gas fresh for up to 2 years. The most important thing to do when shutting off a generator is to RUN THE CARB DRY. turn off the fuel valve at the tank and let the generator stall. if fuel is left in the carb for an extended perod of time it will gum up and clog your carb. Old fuel+clogged carb=no start. Even if stabilizer is used you should run it dry. The best way o hook these up are to the panel, then just turn off your main breaker so as not to backfeed into the grid. Natural gas or propane(providing you have a large enough tank on the property is the best way to go but can get pricey.
this is an understatement! while i dont use stailizers i know that withing 1 month todays gas does degrade but if you shut off the fuel and just run it dry by leaving it on till it stalls*easy way* or draining it you will have no problems your fuel line should have a filter to catch any debris if it doesnt put one on it helps the novice person so u dont have to clean the bowl of the carb as it should catch it befor it gets there. so let me repeat this as most shops will charge 60-75 for a carb clean/tune up, dont leave fuel in the carb unless your using it and once a year change the oil its as easy as opening a soda bottle open drain fill 5 min tops, just watch how many hours its in use vs when it needs a change just like a car.
really do reviews on the gen that your looking at, after useing several honda are my 1st pick if you can find a place that has them ready to go listen to them the sound alone might sell u kinda like a drag car vs a road car huge sound decibel difference.
i think all your ?s were covered an some if not shoot away