Whether it's your main occupation or a side business, you should have proper insurance that will protect you.
The basic policy for an electrician, drywall, painter or other similar business will give you liability coverage and business property coverage.
You often travel with a large amount of tools and building materials. You may also occasionally rent equipment to help on different projects. You may also leave building materials at the job site overnight or over the weekends until the job is finished. You'll have coverage for all of your "stuff". Make sure you carry an adequate amount of coverage. You want to make sure you are able to buy new equipment in the event of a loss.
If you injury someone or damage something while doing your job you'll have liability coverage to protect your business. If it's a serious injury and you are sued, you'll also have an attorney to protect your business assets.
If you have any employees, make sure you have workers compensation.
Don't forget also, that if you are using your vehicle for business use, to have it insured as business use. Failure to do so could result in a denied claim.
For more information on insuring a small business, click here.