I think the first 5 units (or most powerful 5 units) shouldn't cost maintenance.
This would encourage early strong play, on a limited scale, which is both a natural counter and healthy alternative to zombie spam.
Otherwise the only way to stay at 0 taxes and have a decent military is zombie spam.
With the 5 free units, you both encourage a starting party of 5 decent units so that you can start leveling your Champion or Sovereign, but also you allow yourself enough power to counter those that still zombie spam.
For beginning weapons, I'd say Club (2 attack) 10 hammers. Slingshot (1 attack) 15 hammers. and Stone Axe (4 attack +1 crit) 18 hammers.
Then at Standing Armies tech, you can get spear (5 attack) 15 hammers. Staff (3 attack) 10 hammers. and Shield (2 defense) 10 hammers.
-> you should be able to equip spear with shield, at a loss of 1 attack.