Hi steven, I have been doing car valeting for years also carpet cleaning. You will need a wheel cleaning chem, acid is good if really dirty or a non acid one, TFR, a wash and wax for general washing if they don't want it polished. At least one wax polish with a cut in it (used car polish.) A hard surface cleaner for interior trims, a degreaser for removing gum and stickers, glass cleaner, tyre dressing, a spray sheen is useful for putting a shine on trim. Obviously a pressure washer (cold) I use a Kranzle, found them really good and long lasting, a hot water extraction machine for seats and carpets. That will do to start you off.
Autoglym stuff is good and recognised by the public if a little expensive. You are sure to find a local chemical supplier, you will soon learn what is good and what not. Best of luck.