Complex sentence: Shortly thereafter, the house contiguous to his own along the Via della Vigna Nuova, owned by his mother passed into Rucellai's hands and then (c.1460) the house adjoining his mother's was added to the growing residential complex.
Split into simpler sentences: Shortly thereafter, the house contiguous to his own along the Via della Vigna Nuova, owned by his mother, passed into Rucellai's hands. Finally (c.1460), the house adjoining his mother's was added to the growing residential complex.