Do you a hobby or area of interest that you could practise making a website? I would recommend that you don't do the being very green and taking on paid work unless the customer is clear how green you are and you both agree to a price or barter of services. Otherwise you can design and refine a hobby site so you have something to show and you put in reps to learning what will be needed to do 'paid work'. This will also help you determine price because you will no a little more about what does and doesn't take a lot of time.
It is good that you are thinking about doing this and not just jumping in before asking questions, but you want to be sure you deliver what you promise and how do you know what to promise if you haven't done it very much or at all? I don't think you can make promises with an absence of experience.