Ive read some posts discussing that after a while, trade and gold become abundant. In my recent game, as Spain, it has become obvious that Genoa is the object of my post.
It slowly entered a war against HRE, and took over some of the northern italian cities. Then it made peace and went to war with Venice and took all of northern italy except venice.
Now its basically taken the entire peninsula, except for Salerno and Napoli, which belong to me, and Sicily. Currently its liberating fights against Spain, Freance, Sicily and Hungary with crusades on its territories and still expanding, growing, taking territory in France and elsewhere. The graphs show that its financial problems have not stopped it, since it doesnt have trading partners, and its military continues to expand along with its production.
Basically, it has 5 full stacks in the peninsula and around 3 more fighting north. It can't be stopped. My economy as Spain is slow, I only have two cities from which to recruit while I build up a navy to fight the Genoese navy and then eb able to get troops from Iberia to Italia and try to beat this bastard..but it seems impossible with its capacity to simply remake full stacks in 2 turns..