Is there a dollar amount where you legally have to register as a business?

[x_kookoo4kokopuffs_x]

I am a young dude trying to start my own business. As of right now, I buy items, refurbish them, and resell them for more. I've started with nothing, so its a slow a long process. Right now, its also my main source of income, so im only making about $50-$75/week. I am however, putting about 70 hours a week into this. Don't get the wrong idea, it is progressing nicely, just very slowly.

So my question is, when, and how do you register your business when you don't make much to begin with? Can I wait until I am more successful?

Also, is there a way that I can claim all the work I put into my business as work towards social security credits once I register my business?