The economy is offering everything it’s got — high employment, low interest rates, healthy home price appreciation — and still there’s only modest growth in existing home sales. Buyers simply cannot find the homes they want at prices they’re willing to pay, and many are sitting on the sidelines instead. Part of the problem is inventory, which fell again in October: A lack of entry-level homes means newcomers to the market can have a hard time getting a foothold. They and other budget-conscious shoppers shy away from prices in many of the country’s most populous areas, creating a nation of would-be home buyers who show preternatural patience in waiting for the right home to come along.