Just wondering if anyone knows what the rules are if i want to employ a helping hand when and if i have work say for a day at a time ?

can i pay them cash in hand and do i need a work contract etc

For less than 2k a year no need for AHV.
I did many short contracts, never had a contract however ask except a Swiss Government paid me a pension contribution. We are talking about contracts as short as 4 hours, usually a day or 2 max being a week.

Do you have a source/link setting this out, please?

I don't, but it's well-known, and easy to find, I'm sure. The amount is something like 2,200 or 2,500. Two-something, anyway.

This is from the perspective of the 'employee' rather than employer. No idea if the payer has to declare such payments s/he makes, but the paid person doesn't (below the threshold mentioned).

Thanks. I learnt something.

The AHV/AVS puts out a series of pamphlets. www.ahv-iv-ch

In this one

2.01 Beiträge
Lohnbeiträge an die AHV, die IV und die EO
Stand am 1. Januar 2019

I found the following:

Beiträge auf geringfügigem Lohn

Werden auf einem geringfügigen Lohn Beiträge bezahlt?

Vom massgebenden Lohn, der je Arbeitsverhältnis den Betrag von 2 300 Franken im Kalenderjahr nicht übersteigt, werden die Beiträge nur auf Verlangen hin erhoben.

Personen, die in Privathaushalten beschäftigt sind, müssen die Beiträge in jedem Fall entrichten (siehe Merkblatt 2.06 - Hausdienstarbeit). Von dieser Regelung ausgenommen sind Personen bis zum 31. Dezember des Jahres, in welchem sie das 25. Altersjahr vollenden, wenn das Einkommen pro Jahr und Arbeitgeber den Betrag von 750 Franken nicht übersteigt. Die Versicherten können die Beitragsentrichtung aber verlangen.

Personen, die von Tanz- und Theaterproduzenten, Orchestern, Phono- und Audiovisionsproduzenten, Radio und Fernsehen sowie von Schulen im künstlerischen Bereich entlöhnt werden, müssen die Beiträge in jedem Fall entrichten.

Approximate translation:

Contributions on low wages

Are contributions paid on a low wage?

On wages which do not exceed CHF 2,300 per employment relationship in any calendar year, contributions are levied only on demand.

Persons employed in private households must pay contributions in any case (see information sheet 2.06 - Domestic work). Persons who have not yet completed their 25th year by 31st December are exempt from this rule, if their income per year and employer does not exceed CHF 750. However, these insured persons may demand payment of contributions.

Persons who are paid by dance and theatre producers, orchestras, phono- and audio-visual producers, radio and television as well as schools in the artistic field must pay contributions in any case.

This means that the cut-off point applies to all employees who are neither in the artistic branches, nor employed in private households.

There are advantages to demanding that contributions are paid, because one thereby clocks up “years of contribution” which is the basic actuarial building block upon which pensions are calculated.

Even if one has lost faith in an old-age pension actually happening, it's worth bearing in mind that having gaps in

• a disability pension or in
• a pension for a child of a person with a disability,
• a widow’s pension or
• an orphan’s pension
  and of course, if it materialises
• an old-age pension

can be quite serious, other than, of course, for top-segment earners who are able to make their own, alternative and better provisions.