Well my company does SEO and PPC(I'm actually the adwords guy).
SEO is an ongoing process. You need to have an optimized site yes, but that's just a part of it. When it comes to link building and the rest it's not so easy. Our shortest SEO contract is a year and our SEO specialist says it should really be two years.
PPC though is much more immediate. You can spend as much or as little as you want for whatever time period you want.
To get the most benefit of online marketing you really need to do both at the same time.
You've got mail.