This kind of job pays very well because companies are paying top dollars just to make their website on top of searches. How many months before you can rank up a site and all those site wide links? I just happen to learn the term site-wide links from a friend.
It depends entirely on the competitiveness of the search terms combined with whether or not
the website has the content to support those search terms. I tell clients that real results won't
usually start making themselves felt for at least the first month or two, although I've had some
that took longer and some that took less time.
SEO *can* pay very well, but as with web design, while a lot of companies need it, not all of
them recognize the value of it and as a result can be pretty cheap when it comes to what they
are willing to pay.
Looking into the best way to accomplish what you need. 
