My wife and I are going to open a business this coming year, can we deduct what we have already spent in equipment, or do we wait until its officially a business (2018)

We are now buying computers, office equipment, etc, for a business we are starting after the first of the year. We have not yet applied for a business license and are really just getting started, however the initial investment in material is thousands of dollars. Can we deduct this on our 2017 taxes or do we have to wait until we are officially a business in 2018 and then deduct it on the 2018 taxes, even though it was purchased in 2017? Thus far it is only home office equipment and stock supplies.