* Fitness buffs say brisk walking can do wonders for health * Using music to motivate, he encourages others to step out By Dorene Internicola NEW YORK, Feb 18 (Reuters) - People who believe a healthy lifestyle is expensive should speak to "Papa" Joe Aviance, a Los-Angeles musician who lost 250 pounds using the city's sidewalks as his treadmill, its parks as his gym and a discount store as his health food destination.