Hi, a potential client asks me the price I offered him to make blueprints but I have no idea of prices for the realization of a blueprint ...

How much do you charge for one blueprint?

In addition, it is a small project so I can not charge like a big company.

Thank you for advising me

I'd treat it like most other work, figure out how long it'd take you and quote him a price based on an hourly rate.

what is your time worth per hour? Figure that out and then figure out how long it will take you to complete to the project and charge accordingly.