How does a brother pay zakat on an amount of 500,0 dollars that he invested in a construction project currently under development, where profits or losses will be calculated after five years, and he will not receive any money until the project is liquidated?

Zakat (definition) is obligatory on the principal amount of money with which your brother participated in the project, whether it is completed or not, sold or not. Whenever a year passes (hawl) on the principal amount, the value of the existing building is assessed, and one-quarter of one-tenth (2.5%) is given, even if the value of the building differs from the principal amount, as long as it has not decreased below the nisab (definition) (minimum threshold). You do this every year when the hawl is completed, and if you do not possess the money to pay it, it remains a debt upon you.