Personal experience here...
You need to employ when you are way behind with QUALITY work.
We have even tried overpricing jobs to not get them and guess what we still get um!! 17 new customer so far in September!
No point employing if you have stacked up a load of £100 days as most of that money goes on paying employee, insurance, NI etc etc
As stated by someone above, you need to get a decent round first just for you/1 person. So put any prices up that need going up, get rid of very bad payers (cash flow is key when employing)
Nothing like getting to Friday and only having £300 in you cash box?!
Then dont wait for the phone to ring either buy additional work or door knock, advertise and let people know you can take customers on, 90% of people we speak to say "ive been looking for a window cleaner for ages!
We have employed at various stages over the years (even tried another partner in the company, whole different subject!) never permanent employees and will be looking to this again next year as we now are at the limits of what we can achieve in a month! We know this as 6 day working weeks have happened to just try and keep up, or if rain affects play we are prepared to work Saturdays!