1) Client 2) Customer 3) John 4) Whoremonger 1) Whoremonger 
Whore'mas`ter noun 1. A man who practices lewdness; a lecher; a whoremonger. 2. One keeps or procures whores for others; a pimp; a procurer. 
[n] - a prostitute`s customer 2. [n] - a pimp who procures whores
whoremaster 1. A man who associates with or pays for sexual relations with prostitutes or a prostitute. 2. Someone who consorts with whores; a lecher or pander. 3. A pimp who procures whores for customers; usually, a man, who finds customers for a prostitute in return for a portion of the prostitute's earnings.
noun a prostitute`s customer