In the Office Jim invests $10,000 into a Sports Marketing Business with his friends in Philadelphia. How much of Athlead did Jim buy/invest into?
It's not known.
There is no indication in the show how much Jim made from Athlead/Athleap. The $10,000 investment is the only time money is really mentioned for the company.
With the information given; I don't think it's possible to determine a total portion of the company that Jim is supposed to own. Even if we knew the other investment amounts, I don't think we could really tell what percentage Jim actually owned. Jim had at least partially come up with the idea; and was working as a starting member in the company, so he likely got additional shares due to his crucial role.
In the final episode Season 9 Episode 24/25, the Halpert's do not seem noticeably more wealthy than they did the year before. To me this suggest one of three things:
- Jim did not make much off the sale of Athlead, when it was renamed to Athleap;
- Jim's shares transferred over from Athlead to Athleap; so he didn't really make a profit; but still has equity in the new company; or
- Jim made money when Athlead was sold; but it hasn't had a noticeable effect on their lifestyle.
Sadly this doesn't really tell us much about his share of the company.