Visit visa
A tourist or visit entry permit. It does not permit work, and employing someone on one is not lawful.
Someone in the UAE on a visit visa may be perfectly suitable and genuinely available — but she cannot lawfully start work until a residence visa and a contract are in place through a Tadbeer centre.
The pressure to start "just for a trial" while paperwork is pending is where a lot of households get into trouble. The exposure is the employer's, not only the worker's.
Why it matters
Do not have anyone begin work on a visit visa, however informal the arrangement seems. Start the process, and agree a start date that follows it.
See also
This is general information, not legal advice, and the rules change. Confirm anything you intend to act on with a licensed Tadbeer centre or with MOHRE.