AMA database offers invaluable benchmark cap rates.
D000574:American Medical Association; D019985:Benchmarking / Q000191:economics*; D002204:Capitation Fee / Q000706:statistics & numerical data*; D019992:Databases as Topic; D004470:Economics, Medical; D018588:Fee-for-Service Plans / Q000191:economics; D011320:Primary Health Care / Q000191:economics; D011907:Rate Setting and Review; D013038:Specialization; D014481:United States