I did not remember exactly Jacob's expenses, so read through the link that Nord provided above. Jacob spent something like $5K to $7K, but his wife paid the other 1/2 of the common living cost. By himself, it would have cost Jacob more, but of course it would not have doubled.
I just recalled this RV'er whose blog I followed for a while, before this
article mentioned his lifestyle and launched him to a readership of 1M+ on the blogosphere.
He's a musician in his early 40s who is spending $11K/year living full-time in a small 21' motorhome. His relatively small MH has a stealth factor that allows him to blend in and park in places that larger MHs would stand out and get chased away. He gave up performing, but still does musical arrangement for the TV industry. This independent and remotely-performed work allows him to roam the country, and in comfort of the little MH. Said he made more than $11K/year, but he did not need to spend more.
The $11K budget even includes the premium for a high-deductible health insurance. In case any wants to duplicate this lifestyle, I would like to mention that Chinook, the maker of his small but high-end MH, has ceased operation, but a maker of equivalent small MHs called Roadtrek is still in business. Costs of a new small MH like this can run around $100K, and I guess good used ones may be around $30-40K.
PS. The picture in the article was of his first and older RV. He has since upgraded to a newer Chinook as I described above.