Complex sentence: By the end of the 17th century the estates were being broken up, and many of the existing large houses used as mad houses, with almshouses being built on the land between by City benefactors and guilds.
Split into simpler sentences: By the end of the seventeenth century the estates were being broken up. Many of the existing large houses were used as mad houses, with almshouses being built on the land between by City benefactors and guilds.