It will depend on people's circumstances, there is no way to know without knowing whether working for you will benefit the people without knowing the specific details of your prospective employees. In general the system works to make part-time work pay for people receiving most social welfare payments, but there are those who are not any better off.
As for medical card holders, if they have been in receipt of a qualifying social welfare payment for 12 months they will retain their medical card for three years when they take up employment that pushes them above the income levels, so in many cases losing medical card is not going to be a major concern (at least for the next three years).
There are different considerations like this to nearly all the different kinds of primary and secondary benefits, so without going into the specifics of each scheme it is impossible to give a general advice, but saying that if the employment is for 3 days or under a week, and stays under 30 hours, then people should at least be able to keep any entitlement to Jobseekers and Rent Supplement which are probably the two biggest factors you would want to consider. But then again, not everyone gets rent supplement. You can see the problem in addressing your query already. Its never as straight forward as you think, and there can be some more obscure social welfare payments that you might be aware of.
In general, you need to consider
- the primary Jobseekers/One Parent payment
- the effect on a partner/spouse's payment
- Rent Supplement/Mortgage Interest Supplement
- Fuel Allowance
- Medical Card
- Back to School Clothing and Footware Allowance
- Family Income Supplement
- Corporation/Council Rent and waivers provided to unemployed by local authorities, eg bin charges which vary county to county
And there are others.