1 - why do I say I bought it new? it is a house. It was not new when I bought it.
Basically, because that's the way the program is designed, and the IRS says so. The property is new to "YOU".
2 - why do I say I have always used this 100% of the time for business? I converted part of my house to airbnb so before I started renting it out I was using that part for personal use.
You are confusing space with time.
You may have converted 20% of your floor space to rental property on 7/1/2020 for example. That's 20% of your floor space for 50% of the year.
But, from the date you converted that space to business use (7/1/2020) it was one hundred percent business use, provided you did not use that space for any personal use between 7/1/2020 and 12/31/2020.
