Working disabled people tend to be better off claiming Working Tax Credit. You cannot re-claim ESA once you’re claiming Universal Credit. A change in your income or even a one-off payment can trigger a move onto Universal Credit, so you might be worse off.
Universal Credit is affected by how much you earn. It’s not affected by the number of hours that you work. For every £1 you earn above your work allowance (if you qualify for one), your Universal Credit payment will reduce by 63p. If you make a new claim for Universal Credit, you will not get your first payment for at least 5 weeks.
Universal Credit works in a different way if you’re self-employed.