Some of the most manageable MMORPG engines are:NetGoreEclipse OriginsXtreme Worlds
(I think there is a newer version of Xtreme Worlds, as the creator sometimes checks into IR here, but I can't seem to find his post now)
These engines are mostly GUI based, and I believe the latter 2 have simple scripting engines for things the GUI editor can't do. The former, NetGore, I believe relies on the more powerful, but more complex C# language, although I could be wrong, and it may have a simple scripting engine as well.
All of these would make good choices for a young developer who is fixed on making an MMORPG for a limited audience (but could possibly grow).
Another major concern are art assets. An MMO can take a ton of art to even be workable, but there are plenty of art assets freely downloadable in the forums of those engines, and also at Reiner's tilesets
and a lot of people use RPG Maker sprites (Google for those, and other sprite sets can be found in the engine forums, as well as all over Charas Project