Complex sentence: Soane began his training as an architect under George Dance the Younger at age 15, he joined the architect at his home and office in the City of London at the corner of Moorfields and Chiswell Street.
Split into simpler sentences: Soane began his training as an architect age 15, under George Dance the Younger. He joined the architect at his home and office in the City of London at the corner of Moorfields and Chiswell Street.