So how does that work with karma buy and life modules where the only way to get funds is to spend karma at 1 for 2,000?
Those show us that the OP is right in asserting the bad quality of the rules text of the quality.
for every point of Karma (up to 15) spent to be In Debt, the character gets 5,000 nuyen to spend during character creation.You don't
spend points to be In Debt, you
gain them, because that's what negative qualities do, you get karma for choosing them.
If those
up to 15 points of karma where meant to be spent to gain the promised 5,000 ¥ per point they could have put
depending on the level of the quality in those brackets or even put a clarifying sentence behind telling you that in addition to choosing the quality you also have to buy resources at the given ratio.
The point at which this interpretation clearly falls apart is the following:
You could have the quality at a certain level X, but unless you also buy resources for those 5,000 ¥ per karma you'd have a
quasi-free negative quality. Because then you wouldn't owe any money, meaning no interest to pay and no bruisers to beat you down.