The typical rates in my area are 75-100 for a single wide, 75-125 for a double wide.
The competition in mobile home washing is ridiculous. There are guys that go door to door, soliciting 50 dollar wash jobs. Of course they don't do a great wash job. They usually try to wash the homes using high water pressure alone, without chems. None of them even know how to remove black stains on gutters.
Many of the mobile home park operators around here do annual property inspections. The typical trailer needs to be washed at least every two years to pass inspection. That means in an average mobile home park, there could be hundreds of trailers that have to be washed, or the tenant is monetarily fined.
The tenants are forced to get their trailer washed, and many don't have the extra dollars to spend, so they look for cheapest wash they can find. So a crap job passes for a year because the tenant did in fact get his home washed. And because it never really looked good, it may need to be washed every year. Many only look at price, they don't want to pay for quality. It's a low-ballers haven!
I don't advertise for mobile home washing. I get calls for them, and I quote my price range over the phone. If they want me to do it, fine, if not, that's fine too. I usually have to squeeze them in at the end of the day, so sometimes I don't care that much anyway.