There is so much to know when starting out in modeling. First off you will need to set up a portfolio. That includes, at least some head shots, and some 3/4 body shots and some full body shots. You will need several of each. Also you should put several pictures of the type of modeling that you are wanting to do. For example, if you are wanting to be in fashion modeling you need to to have some of you in several different outfits representing the type of clothing you are wanting to represent. If you are wanting to be a swimsuit model you will need several of you in a swimsuit, and so on.
You do not have to model nude in order to make it in modeling. There are big name models who do not do nude modeling. If someone tells you that you have to be nude to model, they are just trying to extort you. If that is the line of modeling that you want to do that's fine, but if not, please don't let anyone talk you into doing something that you don't want to do, and that you will regret later. There is something called "modeling intoxication" that happens when you shoot with someone, and you haven't been involved in a lot of shoots. This is where you start shooting and the photographer asks you to take off little by little until you are nude. It's only a little at a time, so at first you think "it's no big deal, it's only a shoulder", then you've already done that, and "I still have my bra on, besides it's the same as a swim suit top". That is what the photographer will tell you. I have been there when it happens. Then you start to get more comfortable with having less on. The photographer is telling you the whole time, "You look beautiful, You are so sexy" You confidence starts to go up, and you start getting excited that "this talented photographer thinks I am sexy. This photographer sees beautiful models all of the time, and he/she thinks I am beautiful." Although that may be true, he/she is just telling you that. Let your no, mean, no. Before you know it, you are topless or nude. At the time it's not big deal because you are caught up in the moment and don't realize what you are doing. After the shoot is over, or when you go home, or maybe even the next day you realize what you have done, and you feel ashamed. It's to late. Those pictures are already out there. There is nothing you can do legally to keep that photographer from sending those pictures where ever the photographer wants to send them, because the photographer had you sign a model release that says he can do what ever he wants to do with the pictures. I'm not saying that a photographer that has you sign a model release is always going to try that, because there are benefits from signing a model release, but they will use that to their advantage. And this is regardless to how old you are as a model. Real photographers will get rid of those pictures if you ask them to, and not do anything with them, but there will be photographer that will extort you if you let them. That's the main thing. Don't let there be anything out there, that can be used against you in the future.
Now I want to emphasize that not all photographers are in the business to take advantage of girls or guys who will shoot nude pictures with them. There are a lot of very good photographers who will help you get work, and do what needs to be done to get you that work. So, don't miss understand me, and think I am talking about all photographers. The main thing I am saying is to be careful, and if you don't want to do it before you get there, don't do it at all. If the photographer keeps trying to get you to do something you are not entirely comfortable with then leave right then. Don't worry about them getting mad, and don't think that if you leave you won't be able to get any more shoots. You will get more work, and you will get more shoots. Let the photographer know very clearly that you will leave if you start to feel uncomfortable. And then, stick with it. Again, don't feel bad at all about leaving a shoot if you feel uncomfortable.
You could very easily end up in danger if you are in the wrong place with the wrong person! Please! check on the photographer you are shooting with! Always take someone with you when you first meet, and shoot with a photographer! Preferably take someone of the same gender with you. That will help you and the photographer be more comfortable. Get references from other models he/she has worked with before! If they have shot other models and don't want to give you a way to get references, don't shoot with them. You don't know what happened with those models they shot. All you know is what he/she is telling you, and the pictures you see. Don't just take his/her word for it.