Kailua-Kona has most of the major big box stores like Wal-Mart, Target, Home Depot as well as local companies within a few miles of each other. The King's and Queen's shops 40 miles north offer high-end shopping, but overall the Big Island is not a spending-driven culture.
Be prepared for sticker shock when you buy anything and rent is comparable to the Bay Area. Employment opportunities are scare, but Hawaii also enjoys a low unemployment rate of 4.4%; part of what makes Hawaii difficult is that employers only hire people on-island.
If you're serious about making Kona your home, do your research. Check online for open jobs in your field and find a local address to use in your applications. A car is a must, the Big Island is BIG, roughly the size of Connecticut and Rhode Island combined. Lastly, remember Hawaii-time. Everything moves slower here, but the wait is well worth it.