No – It is not possible to guarantee top spot in the Search Engines as there are too many factors out of anyones control. A well optimised website can expect to achieve page 1 positioning however the quantity of work involved depends on many things, not least the strength of competition for those positions.
Unfortunately, there are people who will offer a guaranteed position 1 in the Search Engines however, they are simply manipulating things. For example you may achieve position 1 for a search term which is barely used or for a demographic which is of no use to your business. These posistions will achieve either very low traffic numbers or high numbers of visitors who will have not interest in using your products or service.