I bought a land at 180.000 $ and built 5 houses on it at 300.000 $ (Total 480.000 $). Then I sold them with the profit. I also have 250.000 $ worth land which I bought by commercial intentions. How should I give the tax (zakat) of these properties?
So long as the houses are sold, you should first give the zakat of your cash.
Because you bought the land with commercial intentions, you should also give the zakat of the land over its actual value.
All of the zakat should be calculated as at least 2.5% of the property. Debts should be subtracted first from the total wealth if there is any.