My plan goes bankrupt very quickly. What did I do wrong?

Often when this kind of thing happens, you just have a bad input somewhere (e.g. adding an extra zero, putting a dollar value in a percent field, etc). A quick way to trace these things down is to look at the yearly summary panel in the plan interface for the first few years of the simulation. If one of the categories looks way off from your expectations, try using the expansion panels to narrow it down to the offending line item(s) and then revisit the corresponding forms.