My policy is through Donegal Group and was secured through a local insurance broker. I carry 150k in replacement cost for tools and such and whatever the minimum General liability coverage is required. It cost about $1500 per year. If you have a commercial insurance broker in your town, I like going local. They can shop the best price. You’ve got to cover your own screwups if you damage an instrument, and loss from theft/fire/storm/whatever. If you have employees, you may be required to carry workers compensation insurance. I am not, but am considering adding it anyway. I have three part-time employees and lease a storefront space for the shop.
Working from your house, though…you should talk to your accountant and set up a space in your home for home/office…it’ll help with taxes, then go ahead and get a business license and set up legit. I repaired for about 3 years before i was required to start collecting sales tax and junk like that. Best to start off legit and organized. I only had general liability insurance when I was working at home.