Two Ways to Earn Money

The Short Way:
(12500G per try, but you need to sit in front of the TV)
What you need - beat Tower of Lost Souls

1. Choose level 60, and pick Xianghua or Kilik
2. As soon as the round starts, back up to the edge of the ring and do a move that leaves you grounded (Xianghua's 1A+B(hold), Kilik's 1B+K(hold)).
3. Roll around as needed, making sure that Algol's line of vision is perpendicular to the edge of the ring
4. Wait for Algol to ring himself out

If you're lucky, you can make 12500G in one minute.

The Long Way:
(10000G per try, but you don't need to sit in front of the TV)
What you need - a controller with autofire functionality

1. Set X (PS3) or A (Xbox 360) as the horizontal slash button (A, by arcade notation)
2. Choose Siegfried in Arcade Mode
3. Leave A turned on

Siegfried will continue to do A slashes, which will eventually beat story mode for 10000G. The cursor will still at Arcade Mode when you beat it, and the default character is always Siegfried.

It takes 10 to 15 minutes to beat the game this way, which means you'll make anywhere from 40000G to 60000G every hour.

Source: 2ch, Soul Calibur Forums

Unlockables - Tower of Lost Souls

Ascending the Tower
1f	Soldier's Hat
Clear stage while taking no damage
2f	Warrior Trousers
Clear stage with no ring outs from either side
3f	Pauldron
Switch with ally more than 2 times
4f	Warlord'S Belt
Perform 3 attack throws
5f	Clergy Clothes
Defeat an enemy with a ring out
6f	Wonder Jacket
Throw an opponent
7f	Warrior Trousers
Clear the stage without missing any attacks
8f	Armor Ring: Ice Mirror
Switch characters twice
9f	Scarlett Blossoms
Guard opponent's attack 3 times in a row
10f	Silver Boots
Guard opponent's attack 10 times in a row
11f	Grim Horn
Defeat all enemies with a critical finish
12f	Magus Cloth
Defeat all enemies with ring out
13f	Pegasus Sallet
Destroy all the walls
14f	Stage: Phantom Pavilion- Seesaw
Perform guard impact more than 3 times
15f	Submissions Belt
Clear the stage using only the A and G buttons
16f	Warlord'S Belt
Clear the stage with 0 time remaining
17f	Arm Bandages
Execute a 5+ combo
18f	Kouchu Kabuto
Stand on all corners of the stage
19f	Longhua Qippo
Switch with ally more than 5 times
20f	Life Gem:Sun
Clear the stage with a critical finish
21f	Longhua Qippo
Voluntarily performed a ring out
22f	Honor Boots
Perform more than 4 counter hits
23f	Frilled Skirt
Guard more than 3 times in a row
24f	Protect Gem:Cardinal Directions
Perform a combo with more than 240 damage
25f	Zhuque Changpao
Throw more than 5 times
26f	Warthog Cuirass
Executed a 10+ combo
27f	Iron Gauntlets
Cleared the stage with no damage taken
28f	Aculeus Suit
Opponent guarded a guard break attack at least twice
29f	Menghu Boots
Switch with ally 5+ times
30f	Spirit Gem
Noniple Heads, Clear stage without guarding
31f	Longming Qippo
Perform 5+ Just Inputs
32f	Vane Mask
Perform a low throw
33f	Battle Dress
Perform 3 attack throws
34f	Power Gem: Warrior Princess
Perform guard impact 3+ times
35f	Warthog Pauldrons
Clear without switching
36f	Parlor Blouse
Clear stage with 0 time remaining
37f	Siren's Helm
Defeat all enemies with critical finishes
38f	Gorgon Fauld
Defeat all enemies with ring out
39f	Kingfisher Greaves
Clear the stage without changing position
40f	Deer Head
Execute a 5+ combo
41f	Minotaur
Perform 5+ Just Inputs
42f	Demonic Gloves
Clear the stage without letting opponents invoke a skill
43f	Repel Gem: Iron Shell
Perform an over the back throw
44f	War Cloak
No ring outs either side
45f	Tiger Lily Kabuto
Defeat enemies without using any skills
46f	Butterfly Salet
Same as above
47f	Succubus Boots
Throw 5 times
48f	Life Dem:Jade
Clear stage with a character equipped with the "invisible" skill
49f	Horns Of Calamity
Clear stage with no attacks missing
50f	Tiger Lily Breastplates
Execute a 10+ combo
51f	Tiger Lily Fauld
Perform more than 4 counterhits
52f	Feathered Wings
Clear stage with a critical finish
53f	Blade Ring: Demon Lord
Defeat all enemies with a ring out
54f	Leviathan Paoldron
Destroy all the walls
55f	Priestess Kimono
Perform 3 attack throws
56f	Leviathan Burgonet
Perform a combo with more than 240 damage
57f	Voodoo Armlets
Voluntarily perform a ring out
58f	Tiger Pauldrons
Defeat all enemies without any skills equipped
59f	Voodoo Greaves
Guard an enemies attack 10 times in a row
60f	Voodoo Breastplate
Clear the stage without switching characters
Descending The Tower
B5	Dark Knight'S Cloak
B10	Blade Ring: Raging Thunder
B15	Lapin Chapeau
B20	Repel Gem:Fox Demon
B25	Succubus Guantlets
B30	Demonic Armor
B35	Demonic Pauldrons
B40	Voodoo Crown

Unlockables - Characters

Angol Fear, Ashlotte, Kamikirimusi, Scheherazade, Shura:
Defeat stage 3 in story mode with default characters

Grey characters (Yoshimitsu, Cervantes, etc):
Purchase in Character Creation mode for 4000G each

The Apprentice:
Play through Arcade Mode with Darth Vader or Yoda

Algol:
Play through story mode who faces him on stage 5