roi is the return of the investment that is the customers that come to your site by clicking the banner that you add in any site and the money that you invest in the ppc to run your buisness
To achieve a positive ROI(return on investment) using google adwords it is important to make sure you are selecting keywords that will populate your business when people are using terms that are more consumer driven than research driven. If you are bidding on research terms, you will be losing a lot of money sending ppl to your site with no intentions of buying. You would want to bid on terms like plumbing contractor as opposed to terms like unclog a drain. In one the customer is looking to contract business, in the other the customer is looking for information to do the work themselves.
You ROI will depend on the cost of your clicks, the margin available before adwords, and how your website converts.
ROI - Return on Investment. ROI is calculated by considering the annual benefit divided by the investment amount.
Do yo have any idea how much starting budget I need to advertise effectively on Adwords to "Turnkey Websites" keyword? It is a competitive niche but not very.