The national organization for the Baha’i Faith, which oversees the landmark Baha’i House of Worship in Wilmette, paid more than $1.51 million on Oct. 3 for a vintage four-bedroom, all-brick, Mediterranean-inspired house on Sheridan Road in Wilmette that is south of its campus. The transaction is the latest home purchase by the nonprofit National Spiritual Assembly of the Baha’is of the United States, which since 2014 now has paid $8.97 million to buy six houses on the block immediately south of its campus. Since it was completed in 1953, the Bah’ai House of Worship — also known informally as the Baha’i Temple — has stood at 100 Linden Ave.