DEAR MISS MANNERS: My husband and I own a condo at the beach with two other couples, dividing up the weeks among us. Our agreement is that, at the end of their week, each couple will leave the condo in tiptop shape — fresh sheets, scrubbed bathrooms, vacuumed carpets, etc. This has worked out well and saved enormously on cleaning fees. During the summer months, my husband and I frequently invite friends to join us during our week. Is it appropriate to enlist the guests in the cleanup if we are all leaving the same day? Some guests have volunteered, unsolicited, to clean their bathroom and cha…