how long it takes to rank is entirely dependant on the competition for the keyword in your area.
If its competitive then yes you could build a website and do the seo yourself, but the amount of time it takes to blog, backlink and hit social media to rank in a competitive area you would be better off paying someone to do that for you if you can afford it.
If you are lucky enough to have little competion you could build an average site with a sitebuilder a rank in a few months