Blue Ribbon means a symbol or indicator of premier quality. This is synonymous with the Blue Riband which is a prize given to the one crossing the Atlantic Ocean in the fastest time with passenger liners.
Blue ribbon usually means something of premier or superior quality. It may also mean individuals or things selected on the basis of their sterling quality or reputation. It may also denote the outstanding condition of a property or any other product or an honor/award given to someone.
Leaving a home in blue ribbon condition means leaving it for buyers/tenants in absolutely mint condition. It means that these homes will need lesser repairs and alterations, attracting home buyers in larger numbers. These homes are not completely new, but they have been maintained, cleaned and left in spectacular condition. Buyers are more interested in buying properties which have been kept in blue ribbon condition, since they can take possession swiftly without worrying about extensive repairs and other renovation jobs.