Obviously nobody who was inclined to lend money to the south. The northern economy during and after the war was as sound and robust as before. Sure it went through cycles of growth and depression but it did that before the war. The union currency was sound and treasury bonds were a good investment. Otherwise it wouldn't have stayed afloat. The confederacy, on the other hand, had a government who fought against taxed even in their 'countries' darkest hour. If they wouldn't vote to tax themselves to save their country then why should we assume they would have in time of peace?
Since the majority of tariff revenue was gone, in 1861 the Federal government began deficit spending just before the war started. This was being financed by the banks in the northeast and mid-west.