This is just a syntax error:
var debtID = setInterval(debtIncrease() { //Sets variable for loop stopping later
I don't know what to advise as a replacement as it really just doesn't make sense. The setInterval()
function takes either a string (don't do that) or a function reference as its first parameter. Your code is neither of those; it's not really anything. It's a function call followed by a block, which in this context is not valid.
Maybe you meant (as a comment on this answer suggests)
var debtID = setInterval(function debtIncrease() { // ...