No. Not permanently anyway.
I seriously doubt it's inexpensive to live that way - nor do I believe they're actually "mobile" permanently. They must have a sweetheart deal in parking that bus most of the year...maybe owning a plot of land where they have hookups for internet and electricity and some off bus storage. I'd have to believe they live in a climate that is 12 month consistently not too hot, not too cold. And also they must own a second vehicle of some sort for getting groceries and supplies etc.
And that's not considering how claustrophobic living with 5 in that confined an area would be.
Me and a hippy gal both with good jobs that can be worked remotely, sure - for awhile at least. Three kids...no fargin' way. And at some point, I'm going to tire of it.