Being a site owner, the number one goal on your list would definitely be to achieve top results for the most competitive search term related to your line of business. While some of the site owners handle the search engine optimization work all on their own, there are others who prefer to outsource the work to a professional SEO company. Until recently, many of the SEO firms would charge you without guaranteeing any results. However, now there is a new breed of SEO services, also referred to as performance based SEO, wherein you are required to pay only when your SEO company is able to provide you with your desired results, and not for the work they have done for you.
The risk associated with other SEO services is that you end up shelling out money only for improvement in rankings and visitors. They do not guarantee you any results on their part. So, basically what that means is you live in uncertainty throughout the process.
A pay for performance SEO, on the other hand, eliminates these risks. Such firms would bill you based on the ranking improvements made by them to your website. These firms usually categorize their packages on different page results such as 30-21, 20-11, 5-1 and so on. So, for example, if your current ranking is 47 and your SEO firm improves your rankings to 32. Even then you would not be required to pay a single penny, as the results did not fall in the aforementioned categories. In addition, you will also be provided with daily statistics and ranking reports, so as to help you keep updated.
For these very reason, performance based SEO firm remains your best bet.
Performance Based SEO Services and Analysis by SEO Company 