Wèile huán fángdài, tā zhōumò hái zài zuò jiānzhí.
To pay off the mortgage, he's still doing part-time work on weekends.
Tips
culture
房贷 (fángdài) is short for 房屋贷款 ('housing loan'). In Chinese cities, mortgages are typically 25-30 years (最长30年) with around 20-30% down payment. The phrase 房奴 (fángnú, 'mortgage slave') captures the cultural anxiety around 还房贷 dominating one's monthly budget.
grammar
还 here is huán ('to return / pay back'), NOT hái ('still'). Same character, two readings — context disambiguates. Watch for: 还钱 (huán qián, pay back money), 还书 (huán shū, return a book) all use huán.
