So many questions about full time living

We lived full time in a 41' diesel motorhome. But we were mobile. With my DH's health issues we had to stay in warm weather all the time. He could not be in the cold. You don't say where you are going to be living. Weather issues could be a problem. Even coaches that are for all climates really aren't. Ours was supposed to be, but air infiltrated around the slides, windows, etc.  In the winter you will have trouble with freezing pipes with sustained temps under freezing. Some people enclose their rigs with straw bales, etc. Full time living in a stationary spot makes more sense in a climate that is more mild, especially if you have pets, that can easily die from overheat in an RV that cannot stay cool enough. If there are other alternatives, like a regular mobile home would be better. One that is built to live in full time. We enjoyed our 15 years on the road, but we were retired and moved if the temps didn't cooperate. Renting an apartment would be a better solution. YOu will have constant upkeep and likely problems as RV's require due diligence to maintain.

you have posted in a section of the board that is for questions/issues with the operation of the board, you would probably get way more people seeing your post if you posted in the right section, for instance under "full time RVers" under the groups heading.

Welcome. You posted this question in the community feedback section which is for issues with the website itself. There is a full timing section you could post there or perhaps the moderators will move it for you and you will likely get more traction on your questions.  That said, your issues are like many Americans. I was listening to a podcast the other day and they were saying that a few years ago, home ownership was capable for about 50% of Americans. Now that number has dipped to about 19%. Wages not keeping up with inflation, interest rates are up, and housing prices have almost tripled in the past 5 years. My Son is 21 and I don't know how he'll ever be able to buy a home. For the most part people choose to be full time RVers and less about necessity. While it can be a cost-effective option, that is not always the case. One of the mean reasons people choose to full time in an RV is to move with the seasons and travel. RVs are full of caveats and concessions. As you are finding, utilities/mechanicals can be an issue in severe weather. RVs require constant attention/repairs. RVs are not built like houses. The codes and requirements are different, so they are less efficient at maintaining heating and cooling. Add to that you are open on all 6 sides, basically hanging in the air. Doesn't sound like you'll be travelling with this RV (you would need a large truck for that), so have you considered a park model or tiny home? They are a little more stationary and as a result perhaps better for full time, stationary living. 

Since you will be in your friend's back yard, that seems like a great offer from your friend.

Thing can go wrong with toilet, plumbing in cold temperature. Heating problems, obtaining propane, and other problems due to freezing weather, etc.

At least you have someone to help if something happens. 

A few thoughts:

 - How much is a cheap apartment locally? A few years of hard use and an RV value is going to go down drastically.

 - You don't say where it is. Living full time stationary in someone's back yard is against code in many areas. You don't want to commit to this and 2 months in a neighbor rats you out to the local govt.

 - What will you do with sewage? Can you connect to the house? Is the house septic system sized to handle the extra load? 

 - Does your friend have a 50amp@240v outlet that is metered? A decent size 5er will pull a lot of juice in hot weather and with 110F temps, you probably want dual aircon units. If they see big electric bills jumping by hundreds of dollars, they may get over being friendly pretty quick.

 - How do you plan to run the furnace in the winter? RVs aren't known for great insulation and if you get a cold snap, you can be going thru 30lb propane tanks every couple days. 

 - Do you have a truck capable of pulling a 5er? For a small unit, you want at least  3/4 ton and once you get above around 12000lb GVWR, 1 ton trucks start becoming preferable. If there isn't a mobile tech able to fix something, taking it into a shop gets expensive if you have to pay someone to do it. Mobile techs usually charge just to show up.

If it's not going to be moving, I would look at park models as they have more comfortable layouts.

It can certainly be done but it's often not as good of a plan as it appears originally.

While I can't guide you on a RV, I will tell you that my wife and I have been living in our 2012 Carriage Cameo full time for many years.  It is less expensive than having a brick and motar home, but you still have up keep and repairs.  We have been able to make it mostly on S.S. watching our expenses.  If you can find a lot that you can purchase and install a pad, electric and have a shed for your things (plus washer/dryer) in the long run it will be less expensive than renting a lot.  Be sure to check the laws of what is allowed in your area of choice.  We live in NC.  By having your own lot, you will also have an investment and you can travel if you wish too.  Your are smart by looking for a 4 season unit.  Even in hot weather the extra insulation will keep your unit cooler.  Good Luck!