Willow10. Disclaimer! I haven't time to read all responses yet! Sorry!
My immediate response is that I am exactly like you! I never ask about people's money! If it is a bill that might affect all the neighbours then I might, I suppose, very tentatively, ask if they would mind my being so rude as to ask, but I can't think of an example.
I suppose if my roof needed doing too and I had a good relationship with someone nearby who had used a roofer, I might ask their advice and would they recommend him? But you get a quotation for a job anyway. (On a recent thread - I still say "quotation". can't bring myself to say "quote"! Similarly cannot say "invite" for invitation either! Sorry! It was another thread!)
To her? I might simply go very vague and say I can't actually remember.....