Snake

Snake hatches from the Snake Egg, a Legendary-rarity egg found in the Desert. Desert is zone 3 of 11 on the normal route; the wiki lists its entry requirement as 10K speed, and the nests there are watched by the Scorpion.

The wiki lists its base income as $3.6K/s, which ranks it 4th of the 8 Desert pets by base rate — Royal Sphinx tops the Desert at $280K/s. Base rate is what a normal-size, un-mutated hatch earns; everything above that comes from the size roll and the colour mutation.

With a colour mutation and no size bonus, the same Snake would earn roughly: Silver ×1.2 ≈ $4.32K/s, Golden ×2.5 ≈ $9K/s, Rainbow ×3.5 ≈ $12.60K/s (multipliers from the wiki's Mutations page; arithmetic is ours). Add a Giant (×3) or Huge (×5) size roll on top and the numbers multiply again.

Hatching it pays a one-off reward of +10.8k Speed, $360k, and the egg takes 2m 30s to grow in the pen. That reward is the reason low-income eggs are still worth stealing early: the speed bonus is what gets you into the next zone.

Legendaries are where a Golden or Rainbow roll starts changing your income bracket; guard the pen.