I’ve had similar requests for help and expert advice over the years.
If I barely know someone, I tend to smile and give a very brief response.
If a person persists, I comment that ‘it’s complicated’ and ‘it’ll take me time to research (or answer) so I’ll have to charge’. That deters most.
If someone does insist, I say ‘I’ll have to consult my diary and I’ll need an immediate large retainer’
Once I met a great young man for what was a terrific first date. He’d done a little research on me and at the outset, enthused about my work and asked me various questions as he wanted to make a career in this area. I answered politely but briefly. Then I deflected by saying “ there’s so much to talk about, so let’s talk over coffee afterwards. I want to spend our time together by getting naked and seeing how compatible we are”.
I felt then that I’d handled it well. He performed as agreed and we were both happy. He didn’t offer me coffee later and we didn’t discuss his career plan further. It was a great date but no repeat.
Other times, people I like and know have asked for help and I’ve obliged. It’s easier with people I know but don’t like: I simply say ‘unfortunately, I have to charge’ and I’ve named a fee of 6-10x what I’d normally charge.