Can I charge for time spent / consultancy?

Greetings,

Is there someway that I can advise beforehand that their request may get a tad technical and result in several hours worh of research. (I guess yes).

Is there someway that I can "yes, can do" but it will cost this much $ ?

I am way over providing free and uncompensated for consultancy.... Just to be shopped about for the cheapest competitor (if even they decide they want a rolls but at the end of the day will settle for a mini minor)?

I would rather not say "you'll be right mate, do what you want!"

Ebay's help function seems to be more about Ebay rather than helping sellers some times,

Any thoughts would be appreciated as I do not think that I am a lone soldier here.

Cheerz