You will start reporting the business on schedule C as part of your tax return for the first year that you are actively engaged in the business. It is not necessary to have income or make a profit, but you must be actively engaged in business activities (soliciting business, working for clients who haven't paid yet, and so on).
When you begin to actively perform the business, you will file a schedule C and include your startup costs. If your startup costs are less than $5000, you can expense them in the first year, even if you have no income, this may result in a net loss that reduces your other taxable income. If your startup costs are more than $5000, you can expense some and spread the rest out over 15 years using a complicated formula that Turbotax will calculate for you. Assets that you place in service will be depreciated according to the usual rules; either standard depreciation, bonus depreciation or section 179, depending on your circumstances and options.
So if you are just getting ready, you probably will wait to report the business on your 2022 return. But if you are actively engaged in performing the business, you can report your startup costs on your 2021 return even if you have not been paid yet.
