on a tight budget 预算紧张

low budget  预算少

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on a tight budget 预算紧张

tight是很紧的意思，budget是预算，on a tight（small、shoestring）budget就代表说，处于一个预算很紧张的状态，言下之意，没钱。

例句

She started her business on a small/tight/shoestring budget and could not afford to overspend.

她开始做生意时预算很少，不能超支。