Domains are what you use to identify yourself to your reader, customers, etc. The price of domains depends on the TLD (the ending like .com or .org). While .com are usually $8 to $15 a year, you can easily get a domain for free.
The best supplier for real domains (not like .co.cc that have two endings) is FreeNom.
You can get .tk, .ml, .ga, .cf, .gq domains for free, although they have to be 4 characters or higher. (e.g. me.ml costs money but itsme.ml doesn’t).
I suggest, after you set up your domains with your hosting service, that you get an account with CloudFlare.
It is free and allows you to make your site secure without buying a SSL token.