If the son is getting SSI disability, receiving assets would affect his disability benefits. If he's getting social security on his own work record, it wouldn't matter what the parents left him as the reception of assets is immaterial to SSA disability. The parents are over 70 so likely getting SSA themselves. If the disabled son was disabled before 22 he should be on his parent's records. If he is getting disabled adult child benefits, the receipt of money wouldn't matter. A trust may be needed in any case just because it sounds like he can't handle money.