[Kereth]

While I agree with KaVir that the implications of the original "necromancer" concept are fascinating, I would point out that origins of any term or concept are not necessarily a canon that needs be subscribed to. Very few fantasy concepts have survived into modern use with more than very slight resemblance to their original forms. Now, that said, I also think modern trends are similarly free to deviate from, although if you go so far from either that you end up with a clan of magical warriors wielding supernatural holy daisies, you might want to stretch into another term entirely.

Now, you've already said that undead will be involved, so let's take up this "not evil" concept in that context. You're playing with the bodies of dead people. This means at some point you've killed someone. Depending on whether or not you live in a world where random executions of large masses of evil beings are readily available, this may make it very difficult for your necromancer to practice their craft while still being a "good guy." I suppose there's taking death row inmates and turning them into zombies, but the fellow who slaughters everyone in the day care center is going to have a much easier time gathering pieces for his creation(s). Now, depending on theme, you may also want unspeakable rites or some other inherently dark magics be required for the animation. If the latter is the case, then yes, necromancers would necessarily be evil. Even without that, though, I think it's perfectly reasonable to assume that, for whatever reason, evil necromancers would be the standard, if not the rule.

You're welcome to disagree, of course, and context and precise details of theme can change a lot.
-Kereth Midknight