A dot com domain name is around $20 a year for the registration but that just gives you the name, you still have to host the actual site somewhere.
A lot of the 'free' site builder sites lke wordpress and wix will offer packages where can refegister a domain name and host your site all in one place but what I usually do is to register my own domain name and then have the registry entry just redirect it to a free wordpress site or to my own server at home (which is why my site is offline right now because my server is powered off).
[This message has been edited by ltlfrari (edited 10-01-2020).]