Looking for a likely expression a maid in 1930s England would use to say she's cleaning or keeping house for someone. Is 'I'm used to doing for an older gentleman' or 'He's clearly used to doing for himself' the right expression?
The expression was so ingrained in British colloquial speech in the 1930s and 40s that "Can I do you now sir?" was a catch phrase for the char lady character Mrs Mopp in the BBC radio comedy ITMA which ran from 1939 to 1949. However no one uses it now. If it was used now it would probably be interpreted sexually.
I have heard this expression. My great-grandmother used to ‘do-for’ Emily Pankhurst so I hope this knowledge is ‘in my genes’!
It sounds odd saying ‘I’m used to ‘doing for’ an older gentleman’ I mean, the ‘used to’ sounds odd. You want to say ‘I’m doing it regularly’? In which case I’d just say ‘I’m ‘doing for’ an elderly gentleman.’ Which already carries the sense of ‘regularly’ because ‘doing’ is continuous.
The ‘doing for’ sounds fine but I think you should put it in quotes as commenters have suggested.
I remember people saying ‘doing for’ in quotes ie with a tiny pause before, denoting that.
I have heard Mrs. Bridges (the housekeeper) say it to the chamber maid, in ‘Upstairs-Downstairs’ a popular long-running serial about ‘life below-stairs’ ie in the servant quarters of a grand home. This could be rich source material for you, if you don’t already know it!
Upstairs Downstairs https://m.youtube.com/watch?v=tXuW9u-CAgs
‘He’s clearly used to ‘doing for’ himself’ seems fine, again, I would put the ‘doing for’ in quotes.