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If your business claims a net loss for too many years, or fails to meet other requirements, the IRS may classify it as a hobby, which would prevent you from claiming a loss related to the business.  If the IRS classifies your business as a hobby, you'll have to prove that you had a valid profit motive if you want to claim those deductions.   See When the IRS Classifies your Business as a Hobby for more details.  

The type of business doesn't matter, but the timing and type of the expenditures do!  Your business starts when you are officially open for business, when you ''open the doors'' so to speak.   Start-up costs are incurred in the planning and development phase.   

• If you start a business, you can deduct the cost of items you purchase, like computers and desks, as well as organizational costs to get your business started such as legal and accounting fees.
• You typically would deduct start-up costs over multiple years rather than deduct their cost in the year they’re incurred.
• For property such as desks and computers, this process is called depreciation. For non-property expenditures such as legal fees, this process is called amortization.
• Start-up costs are typically incurred during the planning and development phase of your business. After that, they usually become operating expenses.

See Some costs don’t qualify as start-up expenses for information on operating costs and the timing of the costs.   From TurboTax Tips - Start Up Costs

Timing matters, too.   “Start-up costs are only deductible if your business does indeed start up, and they have to be incurred during the planning and development phase of your business. Otherwise, after that, they become operating expenses.”    The flip side to this is that even though your business isn’t operational yet when you incur start-up expenses, you can deduct them or begin to deduct them in your first year of business (after you are open for business).