Blanket polices would be the best for you I would think. It covers everything but nothing at the same time. Hope that makes sense. It is a cheap way to go. I say this assumeing you will be useing subs and enforceing the fact that they provide and pay for there own insurance. Just a example I am in Arkansas, a 1 mil (2 mil agg) for general liabity for a installer is 530 a year, a blanket policy to cover the owner of the shop I worked at cost 320 per year, and that covers accident claims from people hurting themselves in the office and warehouse (workers and customers). The best advice is to call every insurance agent you can locate not just the local guys.
Jimmy Jackson
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