ANSWER:
Make him understand that along with his parents you are also his responsibility after the marriage and he should fulfill all your financial needs as he will be questioned about this in the hereafter. Give him references from the Quran and Sunnah in a polite manner and make dua for him to understand this.
The best thing is to keep each spouse’s income and savings hidden from the other one and there should be no concept of joint account. Many wives were devastated when their husbands used their money is such joint accounts to get married to a second wife.