Many people ask me if a will is necessary for them. They believe that they're too young, or they don't have enough assets, or they can't decide who gets their estate when they pass away. A will is important for anyone. I recommend setting up a will as early as possible. A will is always modifiable as long as you are competent to make changes so it's not a problem if you change your mind. It is also recommended that you periodically review your wills to make sure that the terms have not changed. You should also modify your will whenever a significant event occurs in your life (i.e. marriage, divorce, birth of a child).
Wills give you the ability to determine your executor (the person handling the estate) as well as trustees and guardians of minors.
Without a will, your estate is divided pursuant to your state's intestacy statutes. In Pennsylvania, if you have a spouse and children (all of whom are also the children of your spouse), then the spouse keeps the first $30,000 and then gets half of the remainder. If the children are not your spouse's, then the spouse only gets half, with the children retaining the rest. The law is complex so it is best to consult with an attorney. With a will, you get to choose which beneficiaries will get to inherit, and what their respective shares are. Furthermore, you can give specific bequests, such as vehicles, jewelry, family heirlooms, and specific cash gifts to your heirs.