wealthy person; person of means
Refers to someone with substantial assets, often implying inherited wealth or property. Slightly formal; in casual speech お金持ち is more common.
His grandfather was a wealthy person in the area.
Though born into a wealthy family, he leads a simple life.
資産家 means a person with substantial personal assets or wealth, whereas 資本家 specifically refers to someone who invests capital in production or business.
Compound of 資産 (assets, property) and 家 (person, specialist). The exact historical derivation is uncertain, but the word follows a common pattern for describing a person characterized by the preceding noun.