The SEO experts are basically divided in to three types. They are the In-House, Agency, Or Independent SEO Consultant. These are basically three categories and one can hire any one of them depending upon the needs and desire. The in-house SEO consultant is actually a team of consultant. This is because the roles of a SEO expert are vast enough to be handled by just one person.
It is possible that a single person can handle them but then it would take a lot of time in finishing the work. So in case there is a time limitation and of course one would want to get over with the work as soon as possible, an In house team can be the best in such scenario. The in house team becomes a part of the company and works regularly so that no big problems arise.
In case an organisation does not have much to pay to the SEO consultant, then in such cases an SEO agency can be hired. A SEO agency works like a third party and does not stay connected with the organisation once the work is done. They work as an outside member. The disadvantage of such agency is the old consultant keep may leave the agency and a new one can join at any point of time. So this might be possible that one have new people working for them every now and then.
Independent SEOs are not the one who works for in house agencies nor do they work in SEO agencies. They stand alone and they stand strong. They do not undertake many projects. They work as freelancers and can be cost efficient. They tend to cost less than the agencies. Since they are not bound to work in team and they do not take many projects at a time, they are more likely to be in touch with the owner and work efficiently to bring out the best result.