My son and I each claim half on property tax. should we each claim half on the interest income from the lender?

Yes, if you are itemizing your return and own a properly jointly, you would split the property taxes and interest in half if you both are paying half of it.  If one of you are paying more than half, then you would only claim the amount you are actually paying.

Itemized expenses include mortgage interest, gambling losses up to winnings,  charitable contributions, state and local taxes up to $10,000, medical expenses in excess of 7.5% of your AGI and casualty and losses in excess of 10% of you AGI with the first $100 not counting towards the loss.  

Then your total itemized expenses would need to be greater than your standard deduction below in order to benefit from your expenses. 

The 2024 Standard Deductions are as follows:

• Married Filing Joint (MFJ)              $29,200
• Married Filing Separate (MFS)      $14,600
• Head of Household (HOH)             $21,900 
• Single                                                 $14,600                                

Blind or over 65 and MFJ or MFS add $1,550

Single or HOH if blind or over 65 add $1,950

Standard versus Itemized Deduction