Usually (in Canada anyway) the cost for liability insurance is based on your gross receipts. I guess they figure the more work you do, the higher the chance of a claim. Try to keep all your insurance (even home, auto, cottage, boat, snowmobile etc.) with one company (or broker) to take advantage of any multi-policy discounts that are available (they are also more likely to help you out if you have problems). Also be careful of "high risk" types of work ie. chemical applications, commercial snowplowing. I ended up subbing out all of my weedspray and chemical applications 'cause the cost of the insurance just didn't warrant me doing it myself. Also in my opinion, don't try to save money by having too little liability insurance, my fiance is an insurance broker and they have a client who is is still paying for an accident he had in 1984 that ended up costing more than his liability limit. I have 2 million with an umbrella rider that covers me and all my personal "stuff" up to 5 million