Under the terms of your disability income insurance policy, you'll have to wait for a certain period of time after you become disabled before you can begin receiving benefits. Some policies (typically short-term policies) even offer two waiting periods--a shorter one for accidents, a longer one for sickness. Waiting periods under short-term policies generally range from 0 to 14 days, depending on the terms of the policy. Waiting periods under long-term policies are longer, ranging from 30 to 720 days, although a 90-day waiting period is most common.

If you suffer a disability, you'll receive benefits until you recover or reach a certain maximum. By definition, short-term disability policies may pay benefits for up to two years, although many policies pay benefits for only three months, six months, or one year. But long-term disability policies pay benefits for a far longer period--for a few years, up to age 65, or even for a lifetime.

If you can't afford to purchase both, it generally makes more sense to purchase long-term disability coverage. Most disabilities last only a short time, and you may be able to financially survive a short-term disability, even without insurance. However, a long-term disability can seriously threaten your finances if you do not have insurance.