Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- Islam gives due care to financial matters stating numerous rulings concerning earning and spending money of which is Zakah.
2- Every bread earner is highly encouraged to observe his earnings making sure that he/she earns this money via lawful (halal) means.
3- He/she should also make sure whether his/her income is liable to Zakah.
4- As for the kind of Zakah on the money earned, it is called Zakah on money (Zakat al-mal), and it has two conditions; to reach the nisab (the minimum amount liable to zakah), and its ownership for a whole year.
Responding to your question, Prof. Dr. Monzer Kahf, Professor of Islamic Finance and Economics at Qatar Faculty of Islamic Studies, states:
As for the first question, it is not clear to me. Is it monthly or yearly? And what is it used for? Also does the employer give an amount for the employee assuming the latter to rent a house in the location or city of work? If it is paid by employer to employee, any part saved of it, after actual payment of rent if any, is subject to Zakah along with other savings. This is to be added to whatever other Zakatable properties one owns and Zakah should be paid on the day of one’s annual Zakah.
Regarding the second question, this land is purchased for the objective of sale for profit, so it is subject to Zakah. The calculation is as follows: market price on the day of end of Hawl (a complete year) of your Zakah minus the amount that you still owe, which is the future installment that you are required to pay.
Allah Almighty knows best.