Early Game:
* Catching and releasing Pokémon: This is the most basic way to earn money, especially early in the game. You'll get a small amount of money for catching and releasing Pokémon, with rarer or higher-level Pokémon yielding more.
* Battling trainers: You'll earn a small amount of money for defeating trainers.
* Selling items: You can sell items you find or that you've purchased to make a profit.
* Selling berries: Berries can be sold at a small profit. You can find them in the wild or grow your own in your PC Box.
Mid to Late Game:
* Secret Bases: If you have a Secret Base, you can set up a "Prize Corner" which will reward players who visit your base with money.
* Pokémon Contests: Winning contests earns you prize money.
* Pokéathlon: This minigame can earn you a decent amount of money.
* Gambling at the Game Corner: You can gamble at the Game Corner in Goldenrod City, though this is a risky method of earning money.
* Trading: Trading Pokémon can be a way to earn money, especially if you trade rare or valuable Pokémon.
* Breeding: Breeding Pokémon can be profitable, especially if you breed Pokémon with rare or valuable moves.
Tips for Earning Money Quickly:
* Catch and release rare Pokémon: Rare Pokémon, like certain starters, lend themselves well to this method.
* Set up a "Prize Corner" in your Secret Base: This is a passive way to earn money, and you can even customize your prize corner to attract more visitors.
* Participate in Pokémon Contests: Winning contests can net you a substantial amount of money.
* Train and evolve your Pokémon: Stronger Pokémon will earn you more money from battling and catching.
Remember, money is important in Pokémon HeartGold, but don't let the pursuit of wealth distract you from the main goal: catching 'em all!