Revenue have only interest in a return which is accurately prepared & filed. If you have other income which shows that you are able to live off it, then making little or no profit in the early stages of a new business would not attract any undue attention from Revenue. Bear in mind that equipment is not written off against income all at once but rather over its expected useful life. And for tax purposes the allowance is 12.5%pa. So even if you reinvest your profit in equipment you may still find yourself with taxable profits. Sole trader is the simplest way to commence. One can incorporate if the business model justifies it at a later stage.