i am not sure if you mean “you” as in my specific situation, or “you” as in any individual claimant. In my exact current circumstances i think I could earn about £40k before becoming ineligible. If I was renting (and receiving housing element), and/or had higher childcare costs, potentially I could earn more than that and still receive a little. As for other claimants, that depends entirely on their personal circumstances - things like high rent costs, having disabled children etc can increase the amount of UC someone can be eligible for.
Your subsequent questions don’t have a simple answer. Anyone can “choose” to work part time I guess? But there are requirements to claiming UC. Again these are dependent on individual circumstances. When you open a UC claim you are told you have to agree to commitments. There is an amount that most claimants are expected to earn per month. This amount is different depending on - you guessed it - their circumstances! If a claimant earns over this then they are not expected to look for work, or more work. SOME people for example those with under 1 year olds, those with a disability, are not expected to earn this amount.
A single person should be earning £952 a month otherwise they will be expected to intensively work search. A couple should be earning £1530 I think. This isn’t an earnings limit , this is only about the intensity of requirements placed on the claimants. I believe those who are self employed are expected to earn more. It also doesn’t mean that those earning under this will be eligible for help. It depends on children, childcare costs, disability, housing costs and other elements that UC contribute to.
This isn’t a perfect answer to your question because the system is not easy to explain. Basically it depends on circumstances.
I am not an expert on the system, just a claimant so I apologise if anything is wrong.
But the way UC works is that in the majority of circumstances the claimant is usually better off the more hours they work. This may not be the case for the minority (those with very high childcare costs, lots of children, disability) but it is certainly true for the majority.