Five hours a day at $10/hr for two years could have earned him $30,000 (5x10x600, i'm sure he was bartering during weekends too)
His car only worths $15,000.
His car only worths $15,000.
We also don't know what other trades he has made during this time. Judging by the description in the article, he seems to be quite prolific, and has probably also made some money with refurbishing electric gadgets and so on.
And we also learned that he still worked at a sushi bar (but lost the job at some point in time). So he has quite a lucrative hobby, but still did a day job.
No car is an investment, unless you're making money from driving it, ie a limo or rental car.
Porsches have some of the best depreciation resistance in the business, but even they can't resist the pull of gravity that comes with use, and the inevitable production of newer, better models. A pristine, low mileage used Porsche is a good buy, a well-used cheap model is best avoided and admired from a distance.
Not that I'm complaining - I picked up a 97 back in 2004 for about $13k (when I worked at a car dealership), drive it for 2 years, and sold it for $14k. What's nice about the Porsche was that a 97 looked just like a 2006 since they rarely change their body styles. I did have to replace 2 tires though which was like $500. Not cheap to own, but plenty of fun to drive.