You may Not want to add a washer/dryer for several reasons, just give it some thought.
Not only does it take up valuable space, but it also introduces lots of moisture in the limited space that can cause a lot of problems during the cold winter months.
Even though it may be less convenient, it is usually more practical to use the laundry facilities within the park or local Laundromat.
Also most people always leave their water and sewer hoses connected up as you would have to with a washer/dryer. As mentioned earlier, you would have to deal with heated hoses during the cold months.
What I do (w/o washer/dryer) is function from the internal tanks that don't see freezing temperatures.
During a day off, hopefully when the sun is shinning, I dump the holding tanks, refill the water tank, and then put the hoses away. That way there are no hoses to freeze up. Also doing this in the sunny months the hoses last much longer while not always out in the UV rays.
While on the subject of grease caps, I have one more tip.
We have all seen how the grease always pushes past the seal at the spindle. This is only natural as the internal pressure increases with temperature or altitude. On all of my vehicles (except boat trailers) the first time I remove the grease cap, I place it on a hard service with the open end up and with a center punch I nock a pin hole into the center of it. The hole is so tiny that you should only see it when you hold it up to the sun.
Being the hole is so tiny, dirt and water don't pass, only air. So now as the internal pressure would otherwise increase, the air can now escape without pushing the grease past the seal.
In over 30 years of doing this, I have never experienced any ill effect or anymore grease leaking past the seals. I hope that many of you will appreciate this idea.
Just don't do this on a boat trailer, that is where you want to use the "Bearing-Buddy" to keep from sucking in water as you back the hot hubs into the cold water.