If you decide to implement SEO in-house (rather than hiring an expert) then it can technically be free of charge, especially if you choose a website builder that offers strong SEO features, like Wix.
PPC will come at a cost since you’ll pay every time a user clicks on your ad and this can quickly add up. But remember, while SEO may be free, SEO takes up a considerable amount of time and resources, whereas PPC will cost you but you can sit back and let the ad do the work for you.