If your husband doesn't know any Japanese at all and wants a job in finance, he will either have to be a big executive, or lucky enough to land a job with a foreign firm that doesn't require much if any Japanese. Rare but possible. Look HARD.
If you land a job, he can still come and stay on a dependent visa (which permits work with special permission, but only PT work). If he wants to work FT, then he will have to fulfill immigration requirements, which usually means 5-10 years of work experience for non-teaching jobs.
For many of us, long-term is not 2 or 3 years. That is relatively short, but thanks for explaining in detail.