How’s Monopoly City Streets protected against dummy cheat users?

Monopoly City Streets is a rather cool game, and I quite like it. But I wonder how the game system (and thus other players) are protected against dummy cheat users which are just fraud?

Example:

User A buys a cheepo street worth 100k. User B now gets created and buys Cheepo St for 3,000,000. User A now has 5,900,000 Monopoly Dollars. Now User A buys Cheepo Ave for again 100k. Newly created User C buys Cheepo Ave for 3,000,000. User A now has 8,800,000 Monopoly $. Repeat ad nauseam.

How’s the system protected against such a „malicious“ User A, who creates many dummy users (B & C in this case), who’s only purpose in life is to buy a street from User A?