Assuming that SEO is implemented properly and I cooperate with the SEO program, what kind of return on investment (ROI) can I expect to see?

This is a tough question to answer. Factors like industry, competition, budget, and even client involvement can all impact the ROI. On average we see an ROI around 1:10. Meaning, for every $1 in budget spend, the return on the investment is $10. Of course every SEO program and client are unique so you could expect to see more or less than that.