You should always build websites with SEO in mind if you can. The first crawl from Google is the most important crawl. If you get everything right from the start then you are on the right track. If you need to go back and change things and update things, your changes will not be as strong as the original structure and content posted. I am not saying you must not adjust your content and make changes, I am just saying that if you get it right the first time then your content is more trustworthy to Google.