Just to clarify for others reading this thread, "we" don't own a sole proprietorship. There can only be one owner of a sole proprietorship.
Basically, if you were "open for business" in 2018, then you report all income/expenses on your 2018 tax return. Doesn't matter if your income was zero, and/or your expenses were zero. Any expenses incurred prior to being actually "open for business" are start up expenses and are reported as such in the first year you are actually open. It doesn't matter what tax year those start up expenses were incurred in either.