Billionaire Jack Dorsey, 42, has paid $21M for a Sea Cliff house next to one he bought in 2012 for $10M         The chief executive officer of Twitter is doubling down on an exclusive clifftop neighborhood in San Francisco.   Billionaire Jack Dorsey, who co-founded Twitter and Square, a credit card payment service, forked out $21 million for a house next to one he has owned for seven years, according to Mansion Global. Dorsey paid $10 million in 2012 for his first mid-century two-bedroom house in San Francisco’s Sea Cliff neighborhood.   Dorsey, 42, reportedly bought his new two-story house next door in November. According to property records, the Twitter CEO’s newly acquired house has five bedrooms and three bathrooms.   The seller, Hin Land Investment, had purchased the house in 1997 ... 06/25/2019