Below 5th level, a summoned undead would probably be balanced if it takes an action to direct its attacks. At the same time, a skeleton or zombie is a little less than a unseen servant + spiritual weapon, with the latter a 2nd level spell coming into play at 3rd level. Also, the ranger and druid subclasses are getting their first animal companions around 3rd. I think a good compromise for a 1st level spell might be something that stays around for a minute, but takes an action to control. As a 2nd level spell, moving the control to a bonus action should be feasible.I like the reskinning of existing spells to help a budding necromancer. Undead Servant, Skeletal Hand, Find Familiar with more necro-friendly options would be cool. I like a crawling claw, undead animal, or a floating skull.
I am not sure a necromancer would have a full-bodied fighting minion at first level. 5th level is the multi attack level so I guess waiting until you get animate dead is in line with the rest of the rules.