Employing casuals.

Do you have investment properties at all? I only ask because what you are doing is essentially property management - just like an IP property manager does.

My property manager engages trades people all the time for various one-off maintenance / repair jobs. Some of these are sole traders (one guy working on his own), some of them work for companies (where the company is engaged to do the work).

One of my properties is a block of units which has some common area that is grassed. My property manager engages a lawnmower to come regularly.

Cleaning would be the same - doesn't really matter if it's on-call or regular scheduled - it's just another maintenance person you engage. If you're engaging a company who employs multiple staff, you could try and come to an arrangement about exactly who does the work - especially since there is likely to be some training involved in understanding the unique nature of your properties ... however if you're engaging them on-call rather than on a regular schedule, it can be very difficult to ensure that you'll have the person you need available - since they are likely to be busy working on other jobs.

The structure of your business wouldn't matter either I don't think.

I guess the only difference would come if you are instead "employing" someone (on a casual or permanent part-time basis?) versus engaging a third party business. If you have enough work for someone to do - you could look at employment, but then you would be responsible for costs and insurance and such (and potentially superannuation and PAYG tax), whereas if you engage someone operating a business - then they just invoice you and you pay them and they are responsible for all their other costs.