I just started trading from home full-time after taking an early retirement package.
Generally self employed individuals must pay "Self Employment Tax" (Social Security and Medicare), but capital gains you make as a stock trader are not earned income and are not subject to this tax. Of course you will no longer be contributing to your Social Security account, which may reduce your future benefits, but I'd argue that you're better off putting that money to use somewhere else anyway.
I think health insurance is the much bigger HR issue. I live in Canada so I have considerable government coverage, but many of my US colleagues did not take the retirement offer because they could not afford private health insurance. A major illness or accident could wipe you out.
In terms of actually trading, I feel somewhat isolated and I think that the ability to discuss different positions would be helpful ... it's much easier to delude yourself when no one challenges your decisions. I'm experimenting with a sort of journal approach that forces me to record the rationale for my actions, but the jury's out.
Good luck!