My response is based upon 6 years of extended business travel (30k-35k mi/yr) and finally, 3 yrs. of full timing (7k-8k mi/yr) east of the Mississippi and... still employed. While I have spent limited time out west, I've been a fair weather visitor without much concept as to the weather conditions beyond summertime.
What you're asking is difficult to quantify. Your budget of 8k-12k for a reasonably reliable 4 season RV, be it a Class A or 5th Wheel is the stumbling block. To my knowledge, there aren't many Travel Trailers that would be classified as 4 season.
Having traveled up north during the winter on business, I can tell you that most campgrounds are closed and for good cause. While I can make those winter excursions for a week to ten days in a self contained RV with 4 season capability, I'm so glad for the opportunnity to head back south. Without the ability to park on site at a business with at least an electrical hookup, I'm reliant on batteries and generator use. I have to take on potable water from an inside water source and many dump stations are also closed. Plus, my propane bill approaches the national debt.
I see people full timing in a variety of campers, from tag-along Casita's to Diesel pushers and everything in between. But, for the most part, they are highly mobile, capable of following the sun. I wouldn't want to spend the winter months between Erie, Pa and Buffalo, NY even IF there was an open campground.
If your professions are conducive to travel, e.g. traveling nurses or independent contractors in traveling sales you shouldn't find it difficult to generate an income. However, your commitment to an area could vary in length of time. While traveling, I've found that Passport America (note restrictions) offers good savings, as does Fed/State/City&County parks for short term camping. I don't hesitate to use the Federal "geezer" pass for 1/2 price camping. Once settled on a geographical area for work, a monthly rate at a commercial park, with more amenities, seems to be my choice relative to expenses. I can usually find a RV park with a monthly rate falling between $350 and $550/mo. The most popular areas are best visited during their shoulder season.
All this to say, if a 4 season RV is still part of your criteria, you might consider replacing one of the two cars with a '99-'02 Ford 7.3 diesel. Aside from the transmission, they enjoy a pretty darn good reputation... unrefined, but reliable. Next, I'd look for a 30'-32' 5th wheel with 2 or three slides. Excel and NuWa's HitchHiker LS series come to mind as reputable 4 season manufacturers. You're probably looking at model years of '99-'03 in the price range of $15k-20k (See
PPL and
NuWa's Retail Outlet) . Just have enough truck (dually?) to handle the house. Also, you might want to take your second car out of storage to use as a chase car. Many State don't allow triple towing. You both will have transportation for the duration of your stay at each location. Sorry for the long post. But, it may give you food for thought. Good Luck and travel safe.
RVn Full-time