(petitioners borrowed money from a relative of a petitioner with mortgage prepared as security for debt; mortgage not publicly recorded, thus mortgage holder could foreclose upon default, but other lenders not notified of debt such that mortgage subordinated to later mortgages and security interests; petitioners deducted interest paid to lender, but IRS denied deduction based on I.R.C. Sec. 163(h) which denies deduction for personal interest except for qualified residence interest, but debt must be secured by the residence to be deductible; court upheld IRS position on basis that Treas. Reg. Sec. 1.163-10T(o)(1) requires mortgage to be recorded or perfected in accordance with state law).