No you shouldn't. Paying a modeling agency is like saying they do NOT have to do any work. What is there motive to market you if you PAY them ahead of time. Legit modeling agencies only take a percent. There are so many scams, and some agencies that have a nice office and appear to be honest are NOT. Be bold and ask questions, just like the agent will ask questions about you, YOU should ask questions about them.
Think of it like a job interview. They are not just picking you. You are picking them.
I would stick the agencies mentioned in Backstage.com or inside the booklet called The Ross Reports. I would mail your compcards and headshot and become a model business woman about your pursuits. Don't waste your time with shady modeling agencies. Usually the quality agencies DO NOT advertise either!
You have to find them. You have to mail them your photos, compcard, snap shots and if you are short. Meaning under 5'8" you should stick to a commercial print modeling agency which is more open to height but you SHOULD make your own compcard and mail it out to print agencies or talent agencies ( all found in THE ROSS Reports, or backstage.com) and get ambitious because there are agencies that accept models of all heights...you just need to mail your photos to them and it could take a few times before you get a call.