Cheapest priced copy (Ravnica: Clue Edition): $0.35 at Card Kingdom, near mint, their price list as of .
Fire Urchin 
Creature — Elemental · 1/3 · Common · Guilds of Ravnica · #101
Trample
Whenever you cast an instant or sorcery spell, this creature gets +1/+0 until end of turn.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica: Clue Edition | 133 | Common | $0.35 | — |
| Guilds of Ravnica | 101 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 5 October 2018Fire Urchin’s triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.