The Rivian R1T is finally being delivered to buyers and the R1S SUV isn't too far behind. But as we recently learned, those all-electric off-roaders are not Rivian's main future source of income. No, that honor belongs to its upcoming fleet of EV delivery vans for e-commerce giant Amazon.

By the end of next year, Rivian must deliver to Amazon 10,000 units of those vans. Another 100,000 are expected by the end of the decade. With Rivian's IPO is just around the corner, additional details are coming out regarding its relationship with Amazon, which happens to be one of its biggest backers, along with Ford.

Amazon revealed late last week that as of September 30, 2021, it held equity investments "including preferred stock of Rivian Automotive, Inc. representing approximately 20 percent ownership interest" with a value of around $3.8 billion. Last December, that figure was $2.7 billion.

This year alone, Amazon pumped in an additional $1.3 billion into the EV start-up. Ford, meanwhile, has a stake higher than 5 percent. Amazon's major stake in Rivian is both a good and bad thing. The upside is that it shows just how much confidence it has in CEO and founder R.J. Scaringe, his vision, and his products.

The downside is that Rivian has great expectations to meet. If it can't deliver those vans on time, then Amazon won't be happy. If there are quality issues, Amazon also won't be happy. The list goes on. If Rivian manages to pull things off, then it stands a serious chance of becoming the most serious rival to Tesla to date. Elon Musk also recognizes the importance of entering the EV delivery van market, as does Ford. But it seems Rivian will be getting there first, thanks to Amazon.

It's going to have to because despite raising billions of dollars from investors, the company has actually lost money. Hopefully, next month's IPO that's seeking a valuation of $80 billion, will turn things around.