Forgot to say, we had a home-converted camper van insured for a musician's use. I'm fairly sure it was both business and domestic as it was on the same policy as the musician's other car which was certainly for business use. Initially we had to get the van inspected and 'certified' as a safe conversion. To do this we asked the company who had cut the window holes in the van for us to write a testimonial confirming that the conversion was safe . After that the insurance was renewed annually with no further questions asked.

I have to say this was a few years ago, but it was already very hard for musicians to get any kind of car insurance.