"To stretch the budget" means to use money or resources carefully and efficiently in order to make them last longer or cover more expenses. Full definition
I have twins and stretching a budget for one chair is one thing, but for two is quite another. (albeebaby.com)
It's a big difference that really enables me to stretch my budget further. (soapdelinews.com)
Be certain to borrow only an amount in your fast cash personal loan that you can easily repay without stretching your budget too far. (badcreditloanservices.com)