Add a 3.6 Onan Generator LP or Diesel?

Thanks for the great suggestions, Lyle and Dutchman Sport. We are retired but volunteer as emergency medical responders and in case of a lack of electricity here during a disaster we think it would be advisable to be self-sustained. We just been trailering for a year and primarily are full hook-up camping but many state parks in California do not have hook-ups. Our Arctic Fox 5th wheel says we could handle a 3.6 Onan Gen LP. I have no idea at this point what the costs are for that generator/ best place to buy and same with Solar.
Thanks