In Shakespeare's time, women didn't have the same legal rights to inheritance as men. Usually, after a father died, a daughter's husband would receive the inheritance and not the daughter. King Lear devises a plan to coordinate his will before he dies since he has three daughters. Regan and Goneril are the first two daughters with husbands, but Cordelia is the third and remains to be wed. Lear's will is to divide the kingdom evenly between the daughters out of fairness, but also to make sure that everything is in place before he dies to prevent the children from fighting over the kingdom.
This seems logical and a good way to control the situation after death. However, King Lear forgets that this is not a good legal decision for himself because once he gives away his land, title and money, he has nothing! Then he has to live under his daughters' control and will. He thinks this will be fine because he assumes that his daughters love him so much that they will obviously take care of him until he dies. Sadly, he is mistaken. He does try to make sure that his daughters will take care of him before he divides up his land by asking them who loves him the most. But this is foolish because the nature of human beings is very competitive and the girls fight over the idea of loving him the most. The only honest one, Cordelia, is the one he misreads and misunderstands, thereby solidifying one of his tragic flaws.
Summarily, it was a nice idea for Lear to try to avoid a family fight after he died by dividing up the kingdom beforehand, but it only resulted in leaving himself with nothing for retirement as well as blinding himself to the real character of each of his daughters.