Actually Nixon got rid of his Secret Service detail ten years before his death.
Nixon was a practicing attorney unlike Clinton and Obama, so he made his bucks early on during his career. He made more money during WW ll playing poker in the South Pacific. Lt. Cmdr. Nixon was considered one of the best poker players in the Pacific theater during WW ll. By the time Nixon entered politics right after WW ll he was pretty well off.
Also Nixon was an author of many best selling books after his Presidency.
So no slush funds were needed.
Nixon was a very generous person. Ask any one who actually knew him.
Ask any Marine who was White Beach when Nixon would come walking up to them wearing his wingtip shoes while walking along Camp Pendleton beaches. White Beach was his favorite.
Remember the story of Nixon at night at the Lincoln Memorial talking to the hippies ?
I have a lady friend who's father was Nixon's chauffeur after he resigned. When Nixon decided to move from San Clemente to a place where he said "Where nobody likes anyone" that being New York City Nixon gave his Cadillac limo to his chauffeur in appreciation for his services.
Obama compared to Nixon makes Watergate look like an infraction compared to J-walking.