OP - It depends on what sort of structure you are doing it in and your exact situation (so this is just a thought exercise for me, and if you want tax advice, go to a local professional). As I've seen people flip houses personally (and it should usually go on schedule C if they are making a business out of it, as it is generally a non-passive activity), or do it in an LLC (treated as a partnership, if there are multiple owners), or in an S corp. In the partnership or Schedule C, you have to worry about SE taxes on top of income taxes, but that is now mostly offset with the QBI deduction. Otherwise, it is treated as ordinary income for income tax purposes.
In an S corp, you have to worry about running payroll for compensating the officers (which in turn reduces the amount of the QBI deduction).
Granted, there are a number of other considerations, such as: state level entity taxation, if all of the W-2 income is you or your spouse and how close you are to the SS cap (and if so, then you could do it under their name and not be subject to all of the SS of the SE tax portion, due to hitting the SS wages cap). As well as if you want to keep on doing it (and need the equity from the sale to help fund deals) or if you want to use some of it for some sort of self employed retirement plan (which would reduce income taxes, but not SE taxes).