Unlike other games, finding hidden packages in vice city is super rewarding.
Finding a certain amount of hidden packages will reward you with goodies which respawn. These bonuses can give you a significant edge in missions.
You also get $100 for every hidden package you find - and $100,000 reward when you get all 100.
So it is super helpful to get these hidden packages as early as you can.
This is the list of rewards you get after collecting a certain amount:
10 = Body Armor*
20 = Chainsaw*
30 = Colt Python*
40 = Flame Thrower*
50 = PSG-1 Sniper*
60 = Gattling Gun*
70 = Rocket Launcher*
80 = Sea Sparrow Helicopter**
90 = Rhino Tank***
100 = Hunter Military Helicopter***
Reward Location:
*Ocean View Hotel, Vercetti Mansion, & Hyman Condo
**Behind Starfish Island Mansion, & Hyman Condo
***Fort Baxter Air Base
Here is a video of all 100 (Thanks to
GTA Series Videos):
Here is an image showing all 100 (Thanks to
G-Unleashed):
However, you will only be able to collect 40 or so when you first start the game as other islands are closed off until you progress further in the storyline.
But there is a trick which enables you to go to the other islands early. Meaning you can get this trophy and all 100 hidden packages before the first mission.
You can see how here (Thanks to
Badinfos):
Note: This is not considered cheating. So it won't affect your stats or trophies. Though, you may feel like a cheater when you do it :P