You can work while you’re getting Universal Credit, you just need to report your income to them. You’re allowed to earn up to a certain amount (it depends on your personal circumstances as to how much – you can ask your Job Coach for exact figures by asking a question in your Journal) before you start losing some of your UC payment. When you reach that limit, you lose 63p off your UC for every £1 extra you’ve earned.
If you’re struggling to meet rent, you could also seek additional help from your local authority to receive a Discretionary Housing Payment that tops up the housing element of UC to help you meet your rent. I hope that helps!