Hi Chloe,
Builders cleans... mmmm well if thats what you want to do go for it. It tight margins, they always ask for more than what you quoted. sO BE PREPARED for extras.
You will also be working along side other trades, like sparkys, builders, surveyors... they will all get in the way and you will find that you will clean several rooms more than once. So you have to be flexible.
Just advertise that you do builders cleans, you need insurance and PL insurance.
Best to telephone the large companies and ask to speak to the managers that deal with the builder cleans for hiring you.
Also another big issue cash flow... they will pay you but it will probably be 90 days if not more.... you will be agreeing to there T&Cs really and not yours. But you can try to get them to sign yours.
At the end of the clean they will ask for you team 1 or 2 to be another day on site, that you never quoted for. As this is hand over day. Where they go round snagging and you clean up after the finishing trades and just clean requested areas or again special requests.
Hope it helps
Dave