how to select poor employee
my mean how select a person who is poor.
I'm not sure what you mean here. If a person does not have the means to 'look' the part for a position, then you would need to help them out. If you are specifically targeting someone who is poor as a condition of employment, I'm not sure how you would do that other than by observation or other reasonably courses of inquiry.
Most jobs have requirements based on skills, knowledge and abilities. If you are concerned that a person needs to be poor to take your position, my guess is there is an underlying assumption you are making about poor people.
It may be better to challenge that assumption and verbalize the specifics of your assumption to make it part of your job requirements.
For instance if you assume a poor person would be satisfied with a smaller wage because they are desperate to work, why not open it up to anyone of any means and just be up front about the wages for the job. If you suspect someone will not last because they are used to making more money, then challenge them on that issue. Ask the same question in different ways multiple times throughout the interview process. If their answers are consistent then maybe you have someone who can do an excellent job but does not want the pressures that come with higher paying jobs.
Good luck and hope this helps.