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I don't have clients.  I work on my own websites.  Some are retail monetized by sales, some are informational monetized by ads. The best place to start with ads is Google Adsense.  Their website has all of the information that you need and lots of sample websites to learn how itworks.  To make money that way you need to produce content of high enough quality that it attracts an audience or attracts a lot of traffic from search and social.