Children grow up, move out and start their own families. That is the natural order of things. In reality, some children never leave the house. They do grow up, but for a variety of reasons, never stop depending on mom and dad for food, shelter and security. An adult child living at home has a host of problems that begin with failing to leave the nest. The parents also suffer in many ways.
When the child was young, the parents created a set of rules that governed the his upbringing. The rules were meant to protect the child while teaching him how to be a productive human being. Those rules no longer apply to the adult child, creating a minefield for parent/child interaction. Privacy is an issue, as it was when the child was younger, so are curfews and chores. In addition, the child is no longer a minor, but an adult who wishes to be respected as an adult. This also blurs the roles of the adult child and his parents. The boundaries needed to survive the living arrangement are difficult to maintain, if they exist at all. The result is an unhealthy and tense relationship between parent and adult child.
There is an inevitable generation gap between parents and children that can cause problems between two groups. The music, lifestyle choices and relationships of adult children are often much different from those the parents experienced. Any effort to guide adult children onto the "right path" appears to them as prejudice or intolerance. This becomes another area of tension for all adults living in the household.
Some parents never stop the old habits of caring for their child, and the child never moves past the need for such help. The child remains dependent on his parents, causing him to fail to form meaningful adult relationships. The immaturity also shows up in the adult child's quest for employment or lack thereof. Parents enable the child's reluctance to grow up, and in doing so, they are maintaining a dependent for life.
One of the biggest problems that parents of adult children living in the home face is financial. Adult children living at home are a drain on their parent's income, especially when the parents retire and their income is fixed. In addition to food and shelter costs, the parents also are covering the costs of maintenance on a home large enough to accommodate three or more adults and possible grandchildren. The parents inevitably foot the bill for other things, like health care and recreational items, resembling an allowance arrangement. Such a financial burden can place the parent's retirement nest egg in jeopardy, force them to work past their intended retirement age and cause them to take on more debt than necessary to finance the family.