Let's calculate:
1200 mortage + 1250 (debt) = 2450
monthly income : 70K /12 * 0.65 + SS = ~3800 + SS
so effective monthly income is 1350+SS.
If the SS > $2900/month, they will be ok (~3x$1400). The bottomline is ss > 2000, 1400/(1350+2000)= 41.8%
If they do live under their mean, you can take a chance if SS > 1500.
Good Luck.