How much debt must you have to be legally allowed to declare bankruptcy?

Healthy Environment asked: In addition to this law question, I have some ethics questions:
How much SHOULD you have to be in debt to be legally allowed to declare bankruptcy? 0? 10k? 20k? 50k? 100k?

why should debt for a home mortgage, business, or other be cleared during a bankruptcy, but not a studetn loan [...]