Poor analogy; Google is considered an ad company because that is how they get their revenue.

From some Googling, it seems that Einstein made money from being an academic fellow, royalties on inventions, and giving lectures. So he seems like he's a physics guy (although figuring out problems to work on, speaking, politicking, etc. also come into play.)

Maybe if we were considering a situation in which Einstein was growing/producing his own food.

This just in, we all need resources to complete our mission/goal, even if getting those resources takes a lot of our time and effort and isn't directly related to said mission/goal.

Example: I'm saving up so one day I can work for free for NGOs (like Watsi).