Payments are calculated based on the outstanding line balance each month. And, you can always pay off your outstanding balance at any time (however, keep in mind that if you pay off the full amount within the first two years, you may have to repay any bank-paid closing costs (not applicable in Texas).
HELOCs are lines of credit, and monthly payment amounts are not usually fixed.
During the draw period (up to 10 years), you will be required to make monthly payments of accrued interest, plus any principal balance in excess of your credit limit, with a minimum payment of $75.00. Please note that if you only pay accrued interest during the draw period, your monthly payment during the repayment period may increase substantially.
During the repayment period, your minimum monthly payment will be an amount necessary to repay the outstanding balance over the repayment period, based on the APR in effect at the start of this period. If rates increase after the repayment period begins, your monthly payment will increase so that the balance is fully repaid at maturity.