How do I report this as investment property if I don't own it?
For starters, if it's your mother's SSN on the 1099-MISC then "you" don't report it on your tax return. Your mother reports it on her own tax return.
next, for whoever that 1099-MISC is issued to (your mother I assume) they do not have any investment property. It's royalty income that's reported in box 2 of that 1099-MISC. When the program asks you for the address of the royalty property (which I think the wording of that question is very misleading) you enter the physical address of the property - weather the recipient actually owns the property or not.
They are reporting royalty income - not property income. Two totally different things as the recipient of royalty income is not required to actually own the property that produces that income.
