Besides the comments by the others -
A person needs to borrow $XXXXX to build a home. Once the home is built, the loan is changed from drawing to a permanent loan for repayment. Usually, during the construction phase, only the interest on the outstanding balance is repaid, so the likeliness of open credit is usually not built into the notes.
If it were open ended, if there were a principal reduction, then the customer could borrow the money again. The purpose of the limit, is: that is what the customer requested, which would cover the cost of the home, which will be converted into an amortizing mortgage (repayment) loan and the payments would be affordable.
Your chief lender and loan committee sets your bank's policies in compliance with state and federal laws. If they feel it necessary, they could create any loan product not in violation of laws. .
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Integrity. With it, nothing else matters. Without it, nothing else matters.