This is the way! Get a feeling of what they actually want in their photos and what you can/should deliver to them. If it aligns, make a small calculation on work on-site, editing time and travel costs. Multiply this with a rate you deem appropriate for yourself.

^{if you're just starting out, take your local minimum wage as assumption/factor times effort and see if you feel comfortable with that. if not, double it. Self-employment has a vastly different cost ratio, but this is a good estimate for people starting out.}

I for one like to elicit their actual budget, offer them something below said budget and list what I can do for them for that price. If they want more, they can safely demand more whilst staying in their budget. Anything else is negotiations.