The contents of most trusts you create for yourself will be considered available to you in determining your eligibility for SSI. On the other hand, assets of most trusts that someone else creates and names you as a beneficiary of may not be considered to belong to you for purposes of determining your SSI eligibility. If you created and funded an irrevocable trust for your own benefit prior to January 1, 2000, it will be grandfathered, and in most cases its assets will not be considered to belong to you.
Trusts designed to aid a person with special needs are commonly known as "special needs trusts." There are three main types of special needs trusts: the first-party trust, the third-party trust, and the pooled trust. All three name the person with special needs as the beneficiary, but they differ in several significant ways.
A first-party trust is designed to hold a SSI beneficiary's own assets. While the beneficiary is living, the funds in the trust are used for his benefit, and when he/she dies, any assets remaining in the trust are used to reimburse the government for the cost of medical care. These trusts are especially useful for beneficiaries who are receiving SSI and come into large amounts of money, because the trust allows the beneficiary to retain benefits while still being able to use eheir own funds when necessary.
The third-party special needs trust is most often used by parents and other family members to assist a person with special needs. These trusts can hold any kind of asset imaginable belonging to the family member or other individual, including a house, stocks and bonds, and other types of investments. The third-party trust functions like a first-party special needs trust in that the assets held in the trust do not affect an SSI beneficiary's access to benefits and the funds can be used to pay for the beneficiary's supplemental needs beyond those covered by government benefits. But a third-party special needs trust does not contain the "payback" provision found in first-party trusts. This means that when the beneficiary with special needs dies, any funds remaining in her trust can pass to other family members, or to charity, without having to be used to reimburse the government.
A pooled trust is an alternative to the first-party special needs trust. Essentially, a charity sets up these trusts that allow beneficiaries to pool their resources for investment purposes, while still maintaining separate accounts for each beneficiary's needs. When the beneficiary dies, the funds remaining in her account reimburse the government for her care, but a portion also goes towards the non-profit organization responsible for managing the trust.
Given the complexity of this field, any trust should be drafted by an experienced attorney knowledgeable about SSI matters.