There are many disadvantages to trading independently. Many independent traders cannot command the same low commissions received by exchange members and member firms. Trading on your own may also be isolating. At a firm, you have dedicated support teams handling equipment, software and hardware upgrades, and developing/acquiring new trading tools. That is beyond the budget of many independent traders.
It is natural, therefore, that many independent traders consider joining a trading firm. Having coordinated a training/hiring program for a Chicago-based proprietary trading firm, I have some familiarity with the challenges and issues involved in making such a move. Here are a few items for your consideration:
1) Many of the best career opportunities for traders are at large institutions, such as investment banks and hedge funds. These are often very well capitalized and able to invest in training and development of traders. The catch? These organizations like to hire graduates of finance and financial engineering programs. Quantitative and programming skills are in demand. If you're looking to build a long-term career in the financial world, I'd strongly encourage you to consider an MBA program with a finance concentration or a Master's program in financial engineering to provide yourself with the competencies and skill sets that are increasingly in demand. In such firms, you'll be an employee with benefits and a salary.
2) Can you afford to start out by trading your own capital? If so, this opens several doors. There are trading "arcades" that provide you with office space, tech support, equipment, and trading platforms and pass along economies of scale to you. These shops generally can command low commission rates and may or may not pass along some of their own commissions to you on top of monthly fees for the service, rent, and equipment. Note that in this structure, you are a customer of the firm, not an employee. That means no salary and, in all likelihood, no draw against future earnings. The upside is that you keep the lion's share of your trading profits. One nice variation on the arcade is the trader's co-op, in which a few experienced traders go in together to share equipment, office space, and other overhead, but trade their own accounts.
3) Do you need capital to get yourself started? Then you might be looking at a proprietary trading firm, in which you trade the firm's capital. The firm provides you with all equipment, space, tech support, software, and platforms. At some of these firms, you may be charged a commission on top of monthly fees. The firm, because it takes 100% of risk, will also take a good chunk of profits. You may qualify as an employee of the prop firm, which means that you would be eligible for normal employee benefits. A monthly draw against future profits may provide you with some stable income; straight salaries are not the norm.
You'll be more competitive to join a bank or hedge fund if you have the education and internship placement experience. You'll be more competitive to join a prop firm if you already have an independent track record of trading success. The education departments at the major exchanges, such as the Chicago Mercantile Exchange and the Chicago Board of Trade, publish lists of member firms and often are aware of training programs and hiring among these. Googling "Master's of Science in Financial Engineering" and looking into MBA programs with strong finance components (see who is publishing in the Journal of Finance!) will give you leads for training for institutional positions.
The bottom line is that few organizations will take you off the street and put capital into your hands to trade. If you're not an experienced trader with your own capital, my advice is to find a graduate program or a training program within a proprietary firm and learn the business from the ground up. Think about building a career, not just getting a job.