Your original question was not about whether it is worth employing someone, but "what steps need to be taken to legally employ someone for a day or two "...
Legally - as opposed to paying a mate cash which you were not interested in.
I mentioned a few things.
Whether it is more hassle or now does depend.
When I was in the game in a drought stricken regional area, the peak season was very short - perhaps two months - three at most.
When that was over many went back to their 'real' jobs and I picked up their clients, which kept me going well enough until next peak.
I then employed two so as to service those clients during spring. Once Peak season was over, I'd let the casuals go.
I didnt make money on casuals - but that was never the goal - it was to retain the client base during a period I could not service them myself.
In my area, profitability was not about maximizing income in spring, but in evening out the drop in income during autumn/winter - but your circumstances may be different.