If the caretaker has not shown any semblance of responsibility for the adult's lifestyle, Decisions, Career, Relationships, And finances, They must bear that burden, For they raised someone as irresponsible as themselves. The solution is for the caretaker to take some time out of their lives to care for the adult's needs, As well as ignoring their wants. If this adult has no form of relation towards the caretaker, The caretaker must evict and learn from this as a great lesson.
It depends on the situation but in most cases NO. If it's a refusal then a definite no. However if the reason is more due to a major illness/condition that would affect the ability to work (such as cancer, Etc) and/or due to a developmental/intellectual disability* that limits their capability to be able to hold down a job/have one then that is where I differ.
There are some with an developmental disability such as Autism or Intellectual Disability that are able to work, But there are some that are not able to. If not working for this reasoning it really depends on the situation of the person.
If it's due to a refusal then again I still agree to no. Even more so if the person refusing is expecting you to pay for every little thing (food, Being their personal taxi driver, Clothing, Other expenses).
It is perhaps understandable if one needs to regroup after a major illness or a major life event, Such as unemployment because life does happen but the adult needs to be working on themselves and trying to get their life together. This can happen by the adult actually looking for work, Getting job training, Going to school, Going to counseling, Etc. . . The point is that they are at least actively doing something and are trying to get their life together within a reasonable time period. They can also be doing their share of work around & outside of the house.
Not in my house. You live here, You pay your share. This means getting out and getting a job and using your pay to fund your living space. If you want some place to live for free, Ask your parents or friends but I doubt either will put up with your mooching for long.