Can you plan to found a company?
You can certainly use 'found' in that situation, just as you can use 'start', 'establish', 'begin', etc.
found verb (BEGIN)
B2 [ T ]
to bring something into existence:
Found (Cambridge Dictionary)
they planned to found a school of their own
Francis planned to found Fizwizz, an online retail recruitment agency
In 1147, Robert de Beaumont, 2nd Earl of Leicester planned to found a convent
They moved to Athens in 1871 where Syngros planned to found a new bank.
He [Henry VIII] planned to found a college of canons governed by a dean