You can get any size tank you want. I've seen 500 gallon tanks, they probably come bigger than that.
A propane tank rents for $1.00 per year here in Colorado. So get a 1000 or 1500 gallon tank, and fill it twice a year. Run your generator on propane, use synthetic oil and change it once a year; twice a year if that makes you feel better. Buy stove, freezer, fridge, heater to run on propane. Then you will be set.