I will be helping someone with taxes next month, who receives SS disability pay. Is this taxable income?

Maybe. SS Disability is taxed the same way as SS Retirement benefits. See line 20 of the 1040 and the worksheet that's in the instructions.

What sort of investments would be taxable?

I'm not sure what you're asking here. Your friend should have 1099 reports of those transactions which have to be reconciled on the return.

How much interest needs to be worried about if any was in savings?

Anything over 49 cents needs to be reported.

If there are IRA's that are not "available yet" because the person is not yet of age, can they be ignored?

Activities solely within an IRA have no effect on the return.

Phil Marti
VITA Volunteer