Penny doesn't actually gives lots of money if you do task for her. You can find scrap cloth if you search trash bin at flat, apartment, cloth shop or condominium. Lingzhi mushroom can be found at tree stump at city park or forest. It's quite tricky to find since most trees cover the view. Crimson mushroom is not yet available as underground cave is still inaccessible.
If you're looking to earn money, it's the same as what strategy found in Dream City Profitist game. Buy fishing rod from the bum at city park, buy bread from 24 hours shop to make bait, make lots of bait & then go to forest to do fishing. You'll easily make $200 if you manage to catch lots of eel & sell it to chef at sushi restaurant.
Every Dream city game has Easter Egg (excluding DC Office game) where you can get a gold ring or $100 cash if you walk around city park every day.
If you managed to get into fight club, talk to Hugo from 8 pm until midnight to take part in fight. You'll get $100 if you win the fight.