All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
We did not understand the above mentioned transaction and what section does it fall under; it does not fall under an authorization, a Mudhaarabah (a type of partnership), or any other type of the permissible contracts.
However, you may give him the 100,000 to invest it in a permissible way in real estate, according to the known Mudhaarabah formula, provided that he gets a percentage of profit if there is any profit from the sale of the estate, or from renting it. However, he does not guarantee the capital money unless he has transgressed or was negligent.
You may also resort to any other similar forms of permissible investment.
You should ask the scholars in person, and explain to them exactly what you intend to do.
For more benefit on Mudhaarabah, please refer to Fatwa 276166, 354718, 258553, and 94668.
Allah knows best.