We had a 50 amp box installed at our Relaatives for our stay for 120.00 including the box.however there were two 50 amp brekers installed in the breaker box in their garage.
Two breakers should cost about 30-50 dollar, if you have room from them in the service panel wherever it is installed in the home or garage.If not call an Electrician and have him look at it. Might require another smaller service panel.
It is cold at nigher herein the Mohave, and many times the Heat pumps kick out and the furnaces kick in using a lot of propane. Might cost you snd or relative 300.00 but how much would it cost to stay that amount of time in a good RV park. If you sewer access and 50 amp couldn't ask fro more.
No sewer access, gettting a plumber, who knows sewer systems to install an RV fittign aand piece of pie to swer tank or line might cost as little as 200.00 or as much as.....
On 15 amp or 20 amp all yu can run is the refrigerator and lights, and small tv. Whatever you can run on a 15-20 amp single circuit at home,Most kitchens have at least two circuits one per 20 amp breaker such as the kitchen plug ins at home is all you can use in the RV.