Create a free site and do SEO?

I am planning to create my own site which I think the best is Yola. Formerly it is known as Synthasite, where I actually have my own account there which are related to money making services, and in the first place about a year ago, I don't have knowledge about SEO. But right now I do. I now can attach Google Adsense there and some good widgets using HTML code, and also flash videos and banners.

The challenging part is, when I do some SEO for this site, do you think I might get returns on this? Absolutely! But there's a bigger chance if you want to upgrade your domain into a proper name which is $19.95 monthly for Yola. This might have a chance that Google will crawl or spider your site as fast as the free plan only, and SEO could be worth for your site.