Do all that you can to research the probable costs in running a business - especially for costs that can be foreseen. This can be done by researching lease space or purchase space rates and prices, contacting utility companies to get past averages on electric, gas, water, trash, phone, internet, etc for those locations, contacting local employment offices for wage averages and other employment costs, researching rates for several marketing channels that will be used, and contact a CPA to estimate possible tax obligations (local, state, and federal).
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Additionally, new business owners can try to research public information regarding other companies in their industry. While these public companies may be much, much larger than the new start-up, the public companies' financial statements can be common sized (each item taken as a percentage of sales or assets). Then, these percentages can be used to estimate costs items by apply those percentages against your sales estimates. Moreover, these financials can also provide an insight into future growth rates or declines for both sales and expenses.