I used free everything when I started out, free engine (mccodes ver.Lite, domain (sub-domain), hosting). The game was popular in my school, a lot of active players daily. Using all the free stuff gained me experience when owning a game, such as setting up a story line, keeping the economy to a tight scale, and a big factor, security.
If you do go with the free domain, once you have gained a little more experience with running a game, move onto a real domain, one you have to pay for. Which will bring more dedicated text based player to the game, as, in my opinion, a paid domain look more professional, therefore they are more likely to dedicate their time towards playing your game.
Thanks for reading
-sniko