My hubby gives his parents 20% of his income (paying into a weekly committe so that at the end of it my in laws will get a lump sum.) FIL has been working for many years now but both sons contribute. If it was up to my hubby he would give more but is limited due to the fact we are both working and saving hard to pay off as much of our mortgage as we can. He has a lot of love and a deep sense of responsibility to his family which is a quality I’ve always admired.