/u/Skobtsov,

May I ask what materials you have read that gave you the impression that Protestant armies didn't have issues with financing in the early modern period? I'd like to suggest that your impression is incorrect.

From the earliest periods of the 80YW and 30YW, financing was a major issue for Protestants, too. In the 80YW, the difference between Alba's side and William Orange's side is that Alba started the conflict with a big army which was called the Army of Flanders, expecting to be fed through contributions such as tiende pfennig, the infamous tenth penny. When financing was unreliable, the Army of Flanders would mutiny. Alba tried to solve this issue by encouraging the sacking of pro-Orange cities, which then led to a cycle of violence that turned citizens and cities against the Spanish.

William of Orange faced a different challenge, namely that he had to raise an army from almost nothing, relying on loans and his own personal estates. He had supporters both in the Low Countries and in Germany, so at great risk he raised a major army of 30,000 in the summer of 1568. He then sought battle against Alba. Alba wisely avoided direct confrontation, knowing that Orange would not be able to maintain such a large army for long. So he shadowed his opponent while avoiding a pitched battle, until Orange's army was forced to attempt a siege of Liege. This failed, they then marched all over the lower low countries until they disbanded, out of funds and out of faith.

Later in the 80YW, the Dutch Republic was able to rise and take trade away from the Spanish, thus while the Spanish faced increasing finance challenges, the Dutch were able to raise revenues to better match their cost of war.

For the 30YW, I have written how the Swedes also suffer from lack of funding. As they entered the 30YW in 1630, Sweden spent more than its revenue, yet still it didn't go enough to pay all these troops. The Baltic provinces were not able to further maintain such large armies of occupation, to quote Swedish reports they were "laid waste". Swedish setback in Magdeburg, leading to the city's sack in 1631, was blamed on the city's unwillingness to pay for Swedish troops to be mobilized. Gustav II Adolf's letters and declarations mention "fixed contributions, either to the expenses of war or troops, to be maintained at the charges of each members" as he refers to his intended alliance.

Finally, even following its victory at Breitenfeld, Sweden had to re-iterate its needs to France, explicitly stating that Sweden required from the King of France 400,000 Imperial thaler each year, which had to be paid on the continent, such that it was more convenient for payment of troops. All that led to Gustavus' march toward Lutzen, and his death there.

To that end the King of Sweden will take his share of the great burden of the war by bringing an army of 30,000 infantry and 6,000 cavalry at his own expense to Germany and maintaining it there. The King of France will contribute 400,000 Imperial thaler, that is, a million livres tournois, every year, which will be paid and accounted for without fail to the agents of the King of Sweden appointed for that purpose, either at Paris or Amsterdam, as the King of Sweden may find the more convenient; of which one half is to be paid on 15 May and the other on 15 November, each year.

It is not a wonder that in many parts of Germany, they still sing songs about the cruel "Swedes" who would come and steal their gold! The later "Swedish army" was a motley crew of Protestants, mostly not Swedes, whose payment arrears took years to settle in the Peace of Westphalia.

Hope this helps debunk your misunderstanding.