Question 1: Is it ok that I didn't pay myself salary all year since I used all income to build the office?
probably not ok. you evidently had a business in which you were active. the fact that all income was used to build is irrelevant. however, it's up to the IRS, if and when you are audited, to determine what it thinks reasonable compensation should have been. you then have the opportunity to contest their findings but this means tax appeals or tax court and that could get expensive.
Question 2: Does the fact that the office building have to be depreciated over 39 years make me owe taxes on the business income, even though I couldn't pay myself anything?
not really. had you taken a salary the S-corp income would be down by the amount of any salary but from your tax standpoint your tax on the S-corp net profits and S-Corp net income. however, the effect of not having any earned income could affect your taxes - for example possibly no retirement plan contribution.
some states tax S-Corp profits so you could end up paying higher state taxes on the S-Corp earnings.
Question 3: If in 2023, I pay myself back from paid-in capital, are those payments tax free and not considered distribution? What would those payments be called?
as an aside, some states impose a franchise tax based on stock and paid-in capital. additions to paid-in capital are supposed to be reported either within a certain time frame of doing it or annually. I wouldn't know if your state has such a tax. check with a local attorney.
from a tax standpoint, the money taken out is a distribution that reduces retained earnings, not paid-in capital (proper accounting) to be reported on your k-1. taxability depends on your basis in the S-Corp. the money you put in increases your tax basis. have enough basis and they're not taxable but do reduce your basis.
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