ALMOST 200 steps up the hill behind the Choi Hung MTR station lie 51 blocks of squalid huts forming the Ping Shek temporary housing area - the oldest government temporary shelter in Hongkong. About 400 families totalling 2,000 people live in the wooden and tin-sheet huts, some of which are so weak that iron rods are used to support the walls. Having lived there for almost 10 years, most families are used to blocked drains, rats, smelly public toilets and over-crowding. Mrs Cheung Lee Hoi-heung, 32, who moved into her 60-square-foot unit seven years ago, said: ''It is like living in an animal cage.'' The mother of three had her kitchen demolished to provide more space and now shares cooking facilities with a neighbour. The Housing Department has plans to rehouse tenants of the 18-year-old area in three years. The first phase is to start next April.