The Frugal Choice: Sportsman GEN4000
It isn't an inverter generator, so it's a bit loud. But if you want the lowest cost generator that will run at least one air condition unit, your microwave, an electric heater, or a lot of other common devices we all use, and a warranty that you can halfway rely on, this is the best option we know of. And the truth is, even if you don't bring a loud generator to an off grid camping spot, there's a pretty good chance someone nearby will, so why not equip yourself the best you can until you can afford to upgrade.
This is the inverter generator that is all the rage right now. It's so close to the Hondas and Yamahas in quality, performance, and warranty, it's a steal at its current price. The big thing is that you can run it on gasoline or propane. Some anecdotal reports suggest that it won't run some air condition units while running on propane. Others say it has done fine running their ACs. But there is no controversy around the notions that it runs quieter on propane and you're less likely to smell like gas after refueling propane.
Your First Upgrade: Champion 3400 Dual Fuel
Onan units are the king of RV generators. And both Honda and Yamaha make a 7000w model that will more fully power most everything you'll ever try to plug into them. But Onans are super expensive and typically require tedious, professional installation. The 7k units are very, very heavy, use a lot of fuel, and you most likely won't need more than 4500 watts anyway. Hondas and Yamahas are basically interchangeable, both offering similar models at almost every level. But Yamahas tend to be a little cheaper, a little quieter and run a little longer on a tank of gas, so the Yamaha gets the nod here. Get the Yamaha EF4500, and you're not likely to ever want for more.