The IRS considers a single member LLC to be a disregarded entity. Therefore, the owner of the business can not make contributions to the business. Period. Income earned by the business is absolutely no different than income earned by you. It is exactly the same.
Contributions to a single-member LLC made by non-owners is reportable business income and is taxable income for the business subject to both ordinary income tax and the additional self-employment tax if the business has more than $400 of income from any and all sources in a tax year.
Expenses incurred before the business is officially "open for business" are start-up expenses and are claimed/reported as such on the tax return filed in the first year the business "is" open for business. It does not matter in what tax year(s) those startup expenses were incurred either.
