I’m just going to throw this out there, nobody can guarantee SEO results. Search engine algorithms are a closely guarded secret. We do our best to understand these algorithms but nobody knows for sure what they consist of. Because of this, it is impossible and irresponsible to guarantee a position on search engine results.
Companies who offer guaranteed SERP [Search Engine Result Page] rankings often do so because they target a low competition keyword. Ranking number one is great however if nobody is searching for that keyword then it’s a waste of time! Other reasons include poor copywriting, dangerous link building techniques, automated SEO programs, bait for other services or sometimes they’re just generally being deceptive.
When speaking with clients I can say with confidence, after completing competitor analysis, whether they are likely to outrank other sites. It’s an educated guess at the end of the day which comes down to experience. Even after years of experience, I still get caught out from time to time.
In conclusion, nobody should or can guarantee SERP results. Stay well clear from anybody who says otherwise as they are likely to cause more harm than good. Finding somebody who is open and honest is the best recipe for success.