Long-term disability insurance is a type of insurance that provides financial assistance to individuals who are unable to work due to a long-term illness or injury. It is designed to provide a source of income replacement for an extended period of time, often lasting several years or until the individual reaches retirement age.

The eligibility criteria for long-term disability insurance can vary depending on the insurance provider and the specific policy. However, some common eligibility criteria include the following:

1. Age: Most policies have an age requirement, typically between 18 and 65 years old.
2. Occupation: Some policies may restrict the types of occupations eligible for coverage.
3. Health: Many policies require a medical examination or questionnaire to assess the applicant's health and pre-existing conditions.
4. Waiting period: Some policies have a waiting period before benefits begin to be paid out.

It's important to review a policy's specific requirements and terms before applying for long-term disability insurance. It's always best to consult a professional or insurance agent for more information and find the best policy that fits your needs.

Hiring a professional for Long-term Disability Insurance is necessary for several reasons:

1. Expertise: A professional insurance agent or financial advisor has the expertise and knowledge to help you understand the different types of policies available and the benefits and limitations of each one.
2. Tailored Solutions: A professional can help you understand your specific needs and recommend a policy tailored to your unique situation.  
3. Understanding the market: A professional can keep you updated on the changes in the insurance market, as well as any new products or coverage options that may be available. 
4. Compliance: A professional can help you understand the legal and regulatory requirements of the policy and ensure that the policy you select is compliant with the laws in your state.