Hmm.

A quick greater restoration should fix that

The problem is getting an army of undead. If a level 20 wizard uses all their spell slots on reasserting Animate Dead every day, that’s 128 skeletons. They’d presumably be untrained laborers making 2 sp a day, so it’s 25.6 gp a day. You’d be the world’s poorest level 20 wizard.

If you want a proper army, your options are having a whole bunch of necromancers, a Lich using its Lair Actions to regenerate spell slots, the Wand of Orcus, or using Finger of Death to murder people for years. And that last one only gets you zombies.

Edit: It’s 142 skeletons if you’re a necromancer wizard thanks to Undead Thrall giving you an extra pile of bones.

Hmm.

Only if you send them to work somewhere else and have them give you their pay.

If you are their “employer” you can make much more than 2sp per day from them.

A good capitalist can make 10x or even 100x of what they pay their employees off their work.

Also, they work 24/7. Even if they worked for someone else, they’d do at least double or triple shifts, depending if they’re 12h or 8h, netting far more than 2sp.

The problem comes in when the necromancers promise skeletons for manual labor stuff to make society better, then they take public funding and ultimately the skeletons start making soulless derivative art and writing plays/stories that barely (or don’t) make sense.

Without going into homebrew or Wish territory (as the former is table-dependent and the latter is DM-dependent), Finger of Death creates an undead that is permanently under your command.

Being a 6th level spell, a 20th level caster can cast it six times per day (by spending all their higher level slots casting that spell exclusively), which means that, provided you have a steady supply of humanoids to cast the spell on, you could have six undeads per day, or 180 per month. In a year, that’s 2190 undeads, which is itself a small army. Give it some time, and you’d have a small country following your commands.

At that point there are only two problems: time itself (which can be solved with features that increase your lifespan, such as Boon of Immortality), and other people trying to stop you (which can be solved by using your spell slots to make them regret their decision).

Without going into homebrew or Wish territory (as the former is table-dependent and the latter is DM-dependent), Finger of Death creates an undead that is permanently under your command.

Being a 6th level spell, a 20th level caster can cast it six times per day (by spending all their higher level slots casting that spell exclusively), which means that, provided you have a steady supply of humanoids to cast the spell on, you could have six undeads per day, or 180 per month. In a year, that’s 2190 undeads, which is itself a small army. Give it some time, and you’d have a small country following your commands.

At that point there are only two problems: time itself (which can be solved with features that increase your lifespan, such as Boon of Immortality), and other people trying to stop you (which can be solved by using your spell slots to make them regret their decision).

I did list that, but doing the math is helpful. This is less useful for labor, but you could use executions or assisted suicide. If aging in their universe is anything like ours, I imagine there’d be no shortage of good people who’d rather go to heaven and donate their money to charity than spend it supporting themselves as they slowly and painfully die, but even in 3.5 where there were downsides to old age, the worst it got was +3 wisdom and -6 strength. Commoner was a class, so they’d roll ability scores and someone could have a Strength of 4, but they could also level up and improve their ability scores.

The other problem is that they’re making zombies, not skeletons, and there’s no rule that zombies decay into skeletons or anything like that. Though I suppose if we’re playing RAW, there’s no rule that zombies decay at all or are unsanitary.