One common scam is the creation of "shadow" domains that funnel users to a site by using deceptive redirects. These shadow domains often will be owned by the SEO who claims to be working on a client's behalf. However, if the relationship sours, the SEO may point the domain to a different site, or even to a competitor's domain. If that happens, the client has paid to develop a competing site owned entirely by the SEO.
Search Engine Marketing, or SEM, is the method of gaining traffic by purchasing ads on search engines. It is also called paid search and sometimes referred to as CPC (cost-per-click) or PPC (pay-per-click) marketing, because most search ads are sold on a CPC / PPC basis. Like Search Engine Optimization (SEO), it relies on keywords that activate your results into the paid advertising section of the search results page.
After that, you need to make a choice about how to construct an online presence that helps you achieve that goal. Maybe you need to set up an e-commerce site. If you’re interested in publishing content to drive awareness and subscribers, look into setting up a blog. A simple website or landing page with a lead capture form can help you start developing your brand and generating traffic. A basic analytics platform (like Google Analytics, which is free) can help you start to measure how you are tracking towards your initial goal.