there used to be a solution for shopify, where you could be a shopify "partner" - create a building website for your "client" - set up a custom checkout like "funnelbuildr" (when it still had one time fee for lifetime use). That is how i still have some "free" shopify sites.
Also weirdly, i think shopify has some deal with google, because the ranking of my newly created shopify sites increases quite quickly and often goes to 1st place for certain keywords. So that might be worth looking into.
Apart from that for a shopify store the minimum fixed cost is 29 usd/month, which is quite high for many nieche sellers. Especially if you want to have several idle websites that have maybe 10 sales per year. Then better to go with woocommerce.