I am not certain if your SSI check goes down. I don't believe it does.
I agree with Sequoias. You can earn far more money if you focus on a career than you can ever get on government funding.
If you're really concerned about your future, see if you can meet with a financial consultant. They will usually tell you the following:
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1) You develop your financial plan and risk feasibility
2) You create an emergency fund and place it in low-yield (low interest earns you some but not a lot of extra money), high-security, highly liquid (you can take it out and use it quickly) investment vehicles. Sometimes they can be short-term T-bills, Certificates of Deposit, or Money Market Funds.
3) You develop a more advanced, higher-return plan, which usually includes investing in stocks and other high-yield (more money from your investment) investments.
Usually, if you do this, you can end up with LOTS more money in the future. There are also many other investment strategies that can get you quite some financial security. I like real estate, for example, and pay attention to that. I should mention I don't usually like REITs (Real Estate Investment Trusts), though and tend to assign them a small role in my financial planning.
If you need help locating a financial planner, I can point you to some resources in your local area that may be able to help you find a quality planner. Let me know.