Usually 1st level, though occassionally 5th level.
For new players, RMX *should* be a better way to introduce them to the game. By removing a lot of options and streamlining the game, they can simply play and have fun. Later, they'll want more realism, and that's when you move to RMC (It's how I found out about RM, first started with MERP, played for a while, then picked up ArmsLaw and used that for a bit, then eventually just moved over to RM2).
Part of your problem might be the type of characters your players wnat to play out of the box. They don't really exist, so be flexible with the professions. For example, the Mystic who wants to use MA, have him play as a Monk but not with the Monk spells lists, rather the mystic ones. This way he gets some magic, some MA, and it's not much of a waste.
-shnar