If you are in business and trade of flipping houses, then the gross proceeds from the sale are your gross income, and all accumulated expenses throughout the holding period are your "cost of goods sold" (COGS).
1. The gross proceeds that you see on 1099-S are the total sales price. That is what you need to report as your gross income from that sale. You can indicate that it was a flip in the description (see #2). You will just need to add up all the costs throughout the years (make sure that you do not take it as a deduction in prior years) and add them as COGS.
2. There is no separate place to enter 1099-S. Where you've indicated is the right place. In the description, you can put "Flip income".
3. You will report it the same way as property A. See #2.
4. Your beginning inventory for 2019 is the ending inventory for 2018. And that should be the costs accumulated for the property in 2018: purchase price, purchase costs, repairs, insurance, etc. Then you add the costs for 2019 as purchases and enter the ending inventory. The ending inventory is what you had on hand as of 12/31/19 (houses plus expenses for them). The program will then calculate your COGS. Sales price (from 1099-S), less your COGS will give you net income.
5. No, you do not need to do "new business" for each property. Think about it the same way as selling lemonade. You do not start a new business for each glass of lemonade sold.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
