I don't think the US has any obligations on the part of the client for those situations. Banks would have AML (Anti Money Laundering) rules that would require confirming or reporting certain transactions but as an individual you wouldn't have to file any papers yourself.

There is a separate provision[1] that requires the reporting of foreign accounts but I think it's specific to bank and financial accounts. I don't think direct ownership of real estate in a foreign country is required to be reported (as opposed to ownership through a REIT).

[1]: https://www.irs.gov/businesses/small-businesses-self-employe...