Complex sentence: Outer Mission houses originally featured front yards or small planting areas in front of the property, but over the years many homeowners paved over their planting areas, often for the purpose of allowing them to park cars on the sidewalk.
Split into simpler sentences: Outer Mission houses originally featured front yards or small planting areas in front of the property. Over the years, many homeowners paved over their planting areas, to allow them to park cars on the sidewalk.