Your friend just doesn't want to see you go :)
Because he's wrong on both counts.
First, you won't have any trouble going to California later, unless you develop an addiction to Coney Islands or Buddy's pizza. Social connections tend to be by social media anyway, and I must admit by your language I assume you are not already in CA or MI.
Second, Detroit is a tech hotbed -- wait, we need to have the 8 Mile conversation. Because there's the city proper, and then the metro area.
The Metro Area, i.e. The suburbs, has been booming for 30 years+, and has been sort-of hogging the growth for the entire region. You can't throw a rock in Novi (know-vie) or Ann Arbor without hitting a technology company. Medical is huge, mechanical engieering, and of course, the industry that made Detroit famous: Pizza. Dominos, Little Caesers and Hungry Howie's are from the metro, but you'll want Buddy's, which defines Detroit style pizza.
Engineering departments from almost every engine and automaker in the world are also located in metro Detroit, even Indian, Russian and Chinese companies who don't even build cars for North American markets. Why? The critical mass of staff and suppliers, particularly in enginering and prototyping.
The D was the poster child for white flight and urban decay. About 3 years ago it finished bottoming out, cleared bankruptcy and made a turnaround, and now all the cool kids think it's trendy and hip to live in the D - certain neighborhoods anyway. A million people don't move back overnight, so Detroit proper will, for quite some time, be a block by block patchwork of "trendy" and "extreme blight". Not a lot of white collar industry is in the D, and obviously it's in the nice parts.
One more thing: the self-driving car industry is a veritable Manhattan Project, focused in the Bay Area and metro Detroit. If you get involved with that, you could find yourself with a lot of opportunities on both "coasts".
On the cost of living...
Detroit's patchwork makes it harder to price living expenses from afar. If you just push "Detroit" into Zillow, you'll get a box of chocolates. Figure out what city your job is in, check Google Maps traffic at 8am Eastern time on a weekday for what commutes you don't want to be married to, and choose towns nearby. For pricing, put in Berkley as a safe, pleasant working class town, Novi is more upscale, and Huntington Woods or West Bloomfield are downright tony.
Honestly I would recommend renting until you get the lay of the land. If I had to spitball one, I'd say the huge apartment complex at 10 mile and Halstead, right at the I-696/275/96/M-5 hub. Farmington is a decent town, and the whole west side is an easy commute. Most of the job growth is on the west side, Novi, Livonia, Commerce, etc.
The social culture is that almost anyone who is financially able to own a home, does. This marries you to a whole ton of home-ownership expense. You may also need a riding mower and use it every week.
Transport: "Detroit is a great big freeway, put a hundred down and buy a car." If it's an automaker or automotive supplier, hold off on buying the car until you find out if you qualify for the "A-Plan", a steep discount for auto industry employees. This also gluts the used car market.
If your job is with the auto industry, consider using that A-plan for a swap to a marque of your employer. They're mellower about foreign cars these days, but the Prius still pushes buttons: it's thought of as technically lousy, but people still buy it! Anytime automakers do a limited coastal-cities release of a cutting edge car like the Chevy Volt, Detroit is always included for obvious reasons. So if your next stop is urban CA, one of those is fine.
Demand an enhanced Michigan drivers license for easy passage to Canada. Windsor is a long lunch, Toronto is a daytrip and the closest "big city".
Public Transit is purely survival-tier, with shockingly early curfews and a 1-3 mile walk on both ends of most suburban trips. Difficult in winter. The exceptions are a few genuinely transitable enclaves like Ann Arbor, Royal Oak or downtown Detroit. But that depends on your employer also being transitable, and for any random employer, that is highly improbable.
