I feel there should be a prompt or some notification when a user goes to purchase a guild to let them know that they can buy a guild off someone rather then purchasing a brand new one for 2,500fg.
This will help out the users trying to get out of their own guild and make the sale.
This can also save the buyer some forum gold so it will help both parties.
I think it should also be emphasized that once they purchase a guild, they cannot disband the guild. They then have to find someone to sell it to. Yes, I'm sure it states some of this in the site rules, but not everyone reads all the site rules specially when they have the random ideas

Even if they do not prompt them but have a little Tips or Guild FAQs on the same page where you would purchase a guild (Page link
HERE)