If you own property of any kind (personal property or real estate), you need a Will to ensure that such property shall be distributed, upon death, in accordance with your wishes. A Will is the key legal document that ensures your wishes are carried out, especially where there are children/dependants.
Without a Will and upon death, your estate may be in limbo until the government or someone (not necessarily a person you would choose) is appointed as the estate trustee to oversee your assets. This may result in delays, further expenses and/or other complications. Not having a Will can further threaten the well-being of your children/dependants by leaving their fate solely at the discretion of the courts.
Consider preparing a Will upon buying or selling real estate. The nominal extra cost, charged by your lawyer, is usually very small in comparison to the additional costs incurred upon administering an estate where there is no Will.