100 million USD is going to dry up in a few months with a sizable organization, especially when you are new and need to mass purchase equipment and other necessities (such as transportation, food, etc). Heck, constructing a building of medium sized costs tens of millions, depending on the scale it could be more.
@factual_criminal if this is like a game, he probably need mana for summoning and depleting it to recklessy isn't really good, second as a necromancer, you usually need corpses to rise, or like here the bones for his skeleton hounds, the first hound had to beat the undeads before he could summon more