The median home price in South Dakota is $295,000. At 80% LTV, the typical loan is $236,000 at the current 7.00% average rate, producing a monthly P+I payment of $1,570. Total interest over 30 years at this rate: $329,241.
Property taxes in South Dakota average 1.28% of assessed value, or $3,776 per year on the median home. This adds $315/month to your all-in housing cost. When evaluating a refinance, factor in property tax and insurance for a complete picture.
South Dakota has no state income tax, so there is no state-level mortgage interest deduction. The federal deduction still applies on loans up to $750,000 for itemizers.