MOUNTAIN VIEW, Calif.—The RVs started arriving on Continental Circle about four years ago. Now they line one side of the half-mile-long street in this Silicon Valley suburb.

Across the Western U.S., rising home prices have pushed more people who can’t afford houses or apartments to live in vehicles, including RVs. In Los Angeles, 16,500 people called a vehicle their home last year, according to local counts. In San Francisco that figure was 1,800, up 45% from 2017, and in Santa Clara County, which includes Mountain View,...