Its more fun to figure these out by yourself. But here ya go.

Buyable Ending Easter Egg:
Step 1: complete all soul collectors
all soul collectors are little fuses on the ground.
- location 1: in the power station on the ground in the snow patch
- location 2/3: both are under the transmission towers on the ground
note: each soul collector take 160 zombie souls to finish

step 2: once you finish collecting all the souls
- go to the power station into the teleporter
- buy the ending for 70,000 points
note: if you dont know how to open the teleporter door turn on power, its in the power station building.

---------------------------------------------------------------------------------------------------------------------
Music Easter Egg:
To do this you must find all 3 phonograph, 1 in each house and shoot the record.
ps. music easter egg is replayable

---------------------------------------------------------------------------------------------------------------------
Extra Easter Egg:
Find all three teddy bears in the map and shoot them.
- location 1: Starting house on the second floor underneath the back bunkbed.
- location 2: In mansion on the second floor in the hallway where you cant walk next to some boxes
- location 3: In the power station building on top of the ventilation.
when done go to the pool and will be open with an extra "perk", for 10,000 points everyone gets a max ammo, as well as a bowie knife.