Your characters can be any age at all. Alfred Hitchcock's Three Investigators were teenagers. They're your characters, so whatever you write is good.
I want to join detective agency as a detective.
Detective Naani is really good, you can watch them on tvshack.net
There is no age limit for the game, Carmen Sandiego Math Detective. The suggested age range this game is suitable for however is between the ages of 8 through 14.
Produced in 1973.
1948
no
Goon Detective Agency should be good enough.
made about 1954
Proofhouse.com has sn data.
around 1978
detective Conan
Being a detective is a good idea because it allows you to solve problems that ordinary people can not solve. Somebody who likes mystery and problem solving would enjoy being a detective.