i have seen "lots" (3 or 4) of people lead climb 9trad) after climbing for about a week or so, maybe seconding and TRing about 20 routes in all... as long as you are a) confident in your own ability, b) able to walk the talk and actually BUILD anchors not just think you can build them, then you are probably ready to try leading
Sport leading hell you could try that after a couple gym sessions if you think you got it. Not a whole hell of a lot of skill to learn there. Clip, go, clip, go, lower. Dont forget to read Chuck's link though to remind you of consequences...