I have an early biography of Robert Burns although there is no publication date the book is published by Thomas Y. Crowell & Co. New York: 46 East 14th Street. Boston: 100 Purchase Street. Titled" The Complete Works of Robert Burns" Biography was done by Alexander Smith. In the book he states "In 1766 william Burnes removed to the farm of Mount Oliphant in the parish of Ayr; but the soil was sour and bitter, and on the death of Mr. Ferguson, to whom Mount Oliphant belonged, the management of the estate fell into the hands of a factor, of whom all the world has heard." It gives no mention of the Oliphants but perhaps you could find a sale to Mr. Ferguson. Hope this helps.