The 1930s was a world wide depression and Germany had repetitions that were doubling down on them.
So how in the 30s did Germany afford to build up their war machine?
Here is the FAQ on the Nazi economy
In particular, you might be interested in
"How did the Nazis monetarily fund their military and how was it sizable enough to take on so many large countries?" by /u/vonadler
How did Germany fund their rise out of the depression following WWI, let alone an army to fight in WWII? by /u/Caherdaniel