Several US Presidents were businessmen but presumably relinquished their interests upon taking office.
www.bankrate.com/finance/politics/businessmen-as-us-president-8.aspx
Former president Abraham Lincoln may be credited with helping bring an end to slavery and with being one of our finest presidents, but he failed when it came to running a business. In his twenties, Lincoln opened a general store in Illinois with a business partner. He bought inventories from other stores on credit to try and make a profit by reselling the items. The economy was doing well at the time, but Lincoln's store wasn't. He eventually had to sell his share of the store. When his partner died, he accrued $1,000 in back payments, which led him to declare bankruptcy. His creditors required him to pay them back over a period of 17 years
But it is still not clear what happened to their businesses when they took office, whether or not they left them in the hands of someone else, 'ticking over' ready for when they left.