Man and Woman are dating and decide to flip a house. Woman personally buys the house with cash in 2018. They open an LLC together in 2018 but do not transfer the house in. The house is never lived in, but over the next two years they fix it up and split all costs equally. There was also a large uninsured theft that was reported and documented  in 2019.

Nothing about this house was reported on Woman's 1040, and no fix-up costs were reported on the LLC in 2018 or 2019.

Man and Woman get married in August 2020. Woman transfers the completed house to the LLC in September 2020. No other costs are expensed to the house after it is in the LLC. The LLC sells the house in December 2020.

I need help with:

1. Was anything erroneously reported in 2018 & 2019? Or can all expenses just be added to basis?

2.Woman's contribution basis as of 9/20 transfer? (Purchase price + theft + 50% improvements???)

3. Man's contribution basis at 9/20 transfer?  Would it be 50% improvements?

4. Does FMV of the house at 9/20 (LLC transfer) come into play? Because that would be the same FMV as the selling price.

5. When does theft take into account- is it during the woman's transfer or during the LLC sale?

Any other tax complications that I'm missing due to the dating vs married transition?

Thank you so much for helping me navigate this unique scenario!!