I will add my experience. I have a 38 Foot Forest River Sierra Sport. We lived in it in Colorado at 8600Ft for 3 years. We are a family of 4 Me, Wife, 2 boys 2 and 3 when we started and two medium to large dogs. We actually enjoyed our time in the toy hauler.
Our model is not a "Garage Model" In other words it does not have a separate garage. It is also a little on the plain side compared to many of the new toy haulers. One advantage is that it is kind of a big open box which meant we could put things like kids beds and some plastic stack able drawers to hold the kids clothes. Less permanent furniture made it much more flexible.
Our Sierra Sport is not a 3 season trailer and has exposed unheated tanks. I put a little effort into winterizing using heat tape on the fresh water hose and added a Black tank heating pad. Each winter we had a large rental Propane tank delivered and would get it filled once a month or so. I also added an on demand water heater inline to preheat the cold incoming water. That made the 6 gal water heater last a lot longer for showers. We did skirt the trailer one winter but that did not seem to make much difference really. We saw temps each winter int the -15 to -20 range but usually not for more than a week or so at a time. The months of Jan, Feb most nights were between 0 and 15 degrees. Summers were beautiful.
Overall it was a great experience. During the winters the RV Park basically closed. We were allowed to stay and one other couple stayed but everyone else was gone. It was peaceful and quiet. During the summers we got to know a lot of the regulars and still keep in touch with some. My kids spent a lot more time outside then they do now that we have a house and we did go out to eat more often than we do now. It really was a fun experience.
The RV Park we stayed at had a seasonal rate for the summer and with everything it ended up being around $350 to $400 a month. During the winter the rate was $250 but we had to add electric and propane and averaged around $500 with everything included. Really not bad for a family of 4.
Your experience might vary but we would do it again. It was kind of nice to have our costs so low each month compared to a house. After a while we really got used to it and did not really have that different of a life. Believe it or not my parents and some friends even came up a couple of times for a week or more and stayed in the RV with us. PM me if you have any questions.
EDIT: Resized image to fit the page.