with the right work and prices, having a daily turnover figure of £350 is quite easy to achieve.
To clean 50 properties in a day is possible, its only 8 1/3 houses an hour, but to get a member of staff to do this, 5 days a week for 48 weeks a year, I do not think this is achievable.
The reason, the cleaner will burn out.
Richard are you vat registered?