The media keeps making a huge deal out of how President-Elect Trump might run afoul of the U.S. Constitution's Emoluments clause because of his overseas hotels, etc. But I don't have any historical context to decide whether or not this is fake outrage.
(Google isn't much help since it just decides to bring back ~200,000 pages of Federal tax advice when I punch in what seems like reasonable keywords.)
Not my area of expertise and I don't want to get into contemporary politics (not least because it violates our sub's rules), but the issue is not simply having any overseas investments but rather a matter of scale and the level of involvement in the investments in question.
So to give some examples, FDR owned a large summer-vacation property on Campobello Island in Canada. The ownership of stock in multi-national corporations has made the formation of "blind trusts" to avoid conflicts of interest a relatively normal maneuver for US presidents for decades.
My understanding therefore is that it's not the simple ownership of land overseas that is unprecedented, or overseas investment in a commercial interest, but the level of direct connection between the man, his name-brand, and the scale of the overseas projects that would in fact be historically without precedent in the United States.