The principle of Karma is a lot more complex than most people make it out to be ("good karma"/"bad karma"). Karma has three components. Sanchita (accumulated works), Prarabdha (fructifying works) and Kriyamana or Agami (current works).
Swami Sivananda has described it well:
"Sanchita is all the accumulated Karmas of the past. Part of it is seen in the character of man, in his tendencies and aptitudes, capacities, inclinations and desires, etc.
Prarabdha is that portion of the past Karma which is responsible for the present body. That portion of the Sanchita Karma which influences human life in the present incarnation is called Prarabdha. It is ripe for reaping. It cannot be avoided or changed. It is only exhausted by being experienced. You pay your past debts. Prarabdha Karma is that which has begun and is actually bearing fruit. It is selected out of the mass of the Sanchita Karma.
Kriyamana is that Karma which is now being made for the future. It is also called Agami or Vartamana."
According to Sanatana Dharma (commonly called Hinduism), effects of Karma can be transcended by realization of our true nature as Brahman, or the changeless, timeless principle (aka "God", or the Source of life). Once realization (enlightenment) happens, all karmas fail to bind one to the cycle of rebirth.
What many IMers fail to realize in their over-simplification of the theory of LoA is that they already have set into motion karmas from previous lifetimes which must bear fruit. Every hour we perform actions, and this includes thoughts, which send out energy to the universe, and create fresh karma for ourselves.
So, not everyone who creates an intent will manifest it; the fructifying effects will depend on karmic seeds already sown, which could support or oppose all present effort. In fact, even the desire to manifest greater wealth etc could create much new karma, so while it appears fulfilling in the short term, it only ties us down more tightly to the wheel of life.
Karmic debt certainly does exist. We are all in a state of debt to various degrees to one another, and will encounter people in our lives with whom there is a karmic transaction to carry out, whether parents, friends or enemies.
Read the book
Aghora III: The Law of Karma by Robert Svoboda; it's excellent.