If the purpose of this activity is to build and sell a building, it is not depreciated at all.

Where are you reporting this activity on the tax return?  On Schedule C as a business?

Nor do you 'deprecate' it <w>

Depreciation = the allowable amount to take as an expense for something that has a long useful life, such as real estate (fixed assets), to show it is wearing out a bit over time as you use it for business functions. That's why there is a place to enter the date for "placed in service."

This is not your business fixed asset. This is your Inventory Asset. You are investing in something which, at the end, will not be yours because you sold it. Even if that crosses a year end, your invested value is right there in that project. Until you use it or sell it, it's just "improvement" as inventory.

Hope that helps.