Complex sentence: In the United Kingdom, "trailers" or mobile homes are generally used for one of two purposes: firstly as holiday homes, designed for short-term living; and secondly as retirement homes for the elderly, designed for long-term occupancy.
Split into simpler sentences: In the United Kingdom, "trailers", or mobile homes are generally used for one of two purposes. And secondly as retirement homes for the elderly, designed for long-term occupancy.