It is illegal to work on a visa other than a valid employment visa in UAE meaning you can not arrive in the UAE on visit or tourist visa and work. However, you may arrive on a visit or tourist visa and search for jobs in the UAE. (This is much better than many other countries where in order to work, you can not arrive on visit/tourist visa and look for a job.)
But once your visit visa or tourist visa expires, you will have to exit the country prior to the expiry of visa. On the other hand if you are able to secure an employment, you will still have to exit the country or pay necessary fees to convert your tourist/visit visa into employment visa.
There are applicable costs for this. It happened to me as well. I arrived here on visit visa for 3 months in the year 2005 and was hired by a local bank. (Lucky me!). They did not allow me to work till my employment visa was stamped.
If any employer asks you to start working on visit/tourist visa, he is not complying with the Labour Laws of UAE. You as well as the employer might get into trouble.
If you choose to work without a valid employment visa in the UAE, you:
- Will not be in compliance with the Labour Laws of UAE. Incase of any dispute between you and the employer, you have no say in anything.
- Run into the risk of being fined and deported if caught while working without a valid employment visa. You will also be blacklisted so that you may never return on an employment visa to the UAE.