Mr.Ferguson is secretly Lord Dawlish, a young rich lord with high social status. He only pretends to be Mr.Ferguson, a name he given to himself as it portrays a much poorer man. His reasoning for portraying himself as poor has to do with his hatred for the rich. People like Linnet. Specially, he does not like capitalism and anything associated with it – even though he himself is the exact thing he claims to hate.
Secondly, he proposes many times to Cornelia, but Cornelia refuses to marry him. Her refusal to marry him are most likely due to his low social status, even though, he is secretly rich.