If I was to inherit a lot of money, let’s say a million dollars, from someone, say a family member, how much of that would have to go to God? Since I never earned it myself but was bequeathed it, do I have to give it all to God’s ministries?
No, you would not have to give all of the money to the Church. You could do so, of course, if you wished; but there would be no obligation to do so. You don’t have to earn all of the money you own in order for it to be rightfully yours. Receiving money as a gift or an inheritance is a perfectly legitimate way to obtain wealth.
The only obligation the Church requires of you is to support the Church according to your ability to do so (cf. CCC 2043). If you have recently come into a large inheritance, your personal ability to provide for the monetary needs of the Church has certainly improved, but the Church leaves it to your personal judgment to determine how much of that wealth you will give to the support of the Church.