Check with the Office of Foreign Assets Control at the US Treasury before you help your client buy.
To use the Office's search features by person and country, click Resources on the page and find the feature that fits your need.
Remember, The Office of Foreign Assets Control administers and enforces economic sanctions programs primarily against countries and groups of individuals, such as terrorists and narcotics traffickers. The sanctions can be either comprehensive or selective, using the blocking of assets and trade restrictions to accomplish foreign policy and national security goals.
So, its important to check the Office's Resources frequently as sanctions change and you need to know what the rules are today when working in real estate brokerage.