Can I work while on a visit visa in the UAE and what if I'm caught?

No, you cannot lawfully work on a visit visa in the UAE, and that includes short-term, cash-in-hand arrangements like the one you describe. Working here requires a work permit, and a visit or tourist visa does not carry one. If caught, you face fines, deportation, and the possibility of an entry or work ban that could destroy the very job hunt you came for; the company faces substantial fines for every person it employs illegally, which is why a business asking you to take this risk is not doing you a favour. You would also have no labour-law protection: if they refused to pay your cash wages, there would be no registered contract to enforce, and complaining would expose your own violation. There are legitimate alternatives if the company genuinely wants you: MOHRE offers temporary and part-time work permits for defined situations, and a serious employer can start the normal employment visa process, which can move quickly. If they will not do the paperwork before you start, treat that as a signal about how they would treat you as an employee. If you have already worked informally, speak to a licensed UAE lawyer before anyone reports the arrangement.