Jared Kushner’s investment fund is not especially large by global finance standards. But as he gets it fully up and running, each step is bringing with it ethical issues that would only grow if his father-in-law, Donald J. Trump, should win another term as president.

His $3 billion fund is financed almost entirely from overseas investors with whom he worked when he served as a senior adviser in the Trump White House. He has taken money from government wealth funds in Saudi Arabia, Qatar and the United Arab Emirates, as well as from Terry Gou, a founder of Foxconn, the Taiwan-based electronics manufacturer, whose role in Mr. Kushner’s firm has not been previously disclosed.

In total, 99 percent of the money placed with him by investors has come from foreign sources, according to a filing with the Securities and Exchange Commission in late March.

Mr. Kushner’s firm, Affinity Partners, is collecting approximately $40 million a year in management fees from those investors even before any share of profits earned on investments. He has made 10 investments to date, totaling $1.2 billion, many of them in companies based abroad.

The investments include stakes in the Shlomo Group, an Israeli car-leasing and financing company; Dubizzle Group, a Dubai-based online real estate site; EGYM, a Munich-based electronic fitness company; Mosaic, a California-based solar lending site; and Zamp, an Abu Dhabi-backed fast food company that operates more than 1,000 restaurants in Brazil.

Other investments include two insurance businesses and a software company.