Generally in England at that time Esquire was used of a man who did not have a title but who was a member of the "gentry", a younger son of a minor aristocrat for example, but it was coming into more general use for any respectable man by the mid 19th century. Gentleman means much the same but might be used of anyone who had private means and did not have to work for a living. Mr Darcy in Pride and Prejudice is described as a gentleman. A yeoman was a farmer who owned his own land as opposed to a tenant. The yeoman would have managed his own farm and employed labourers and farm servants. if he could run to employing a farm manager or agent then he would probably be called Gentleman. There were plenty of Gentleman farmers!