What Time2roll said - just go. You don't know your energy needs - or don't tell it, so 101 is going to be long. Start doing it.
120V kitchen devices draw the most energy - microwave, toaster, coffeemaker. Furnace is a close runner-up. If you can use propane stove for cooking and making coffee, and are willing to conserve energy, you are good to go for a weekend in a warm weather even with 1 battery.
$500 can be too little or too much, depends on your goals. For somebody without much knowledge I would consider a portable
100W solar suitcase. It will keep your battery topped up for a few days if you are trying to conserve energy. Spend the rest on the second 12 battery and a "kind of" battery monitor, $40 on Ebay. If your old 12V battery is too old, then get 2*6V.
You'll figure the inverter thing later.
You don't have to carry a generator to camp offgrid. I know that Time2roll doesn't, and he is not living in "survival mode" either. The only thing that is (almost) impossible without a generator is the air-conditioner.