Ranks
Rank 1
Buy for 5% less and sell for 10% more.
Rank 2
Buy for 10% less and sell for 15% more.
Rank 3
Buy for 15% less and sell for 20% more.
Rank 4
Buy for 20% less and sell for 25% more.
Challenges
Rank 1: Buy or sell 25 unique items.
Rank 2: Buy or sell 75 unique items.
Rank 3: Buy or sell 150 unique items.