As others mentioned, you get paid via Paypal, which is an electronic form of currency. You can have it deposited as money into your bank at any time.
I'm an ebay OG, actually did it for a living when I was younger in the late 90's/early 00 when it was *insanely* lucrative with little effort. The medium was still new, people were uncontrollably, compulsively overwhelmed by the ability to buy crap from their living room and, most importantly, the ability to score good, resalable stuff at garage sales and flea markets was still very juicy, unlike today when everyone knows about ebay and prices it there first.
Learned a lot, one bit of advice I can give is that you will probably be disappointed by selling baby clothes, consumer electronics, random household 'stuff' on there. There's just so much of that out in the world, its resale value is next to nothing on ebay.
I agree with others, on baby clothes, I'd try craigslist first.