Bogen, I never ordered any ham equipment via ebay, but I have heard of scientists that have bought lab equipment, so I guess it can be reliable sometimes. It probably all depends on the honesty of the seller. I have bought used equipment at an in-person hamfest, and it always worked perfectly. If it is from a club regular, he will especially not want to ruin his reputation with other members of the club.
I don’t know the current stats on numbers of hams. You can probably get them on the web. A good place is the ARRL regular site and the beginners site hello-radio. They have sample test questions and a wealth of other info. You may communicate either way, by voice or code. I don’t know the stats, but I believe voice must predominate these days. There are license study guides and review books and sites. The test is progressively harder for the higher classes.
In the past, most hams were men. I don’t know the current stats, but you can probably look them up online. I will see if I can find that info.
One interesting thing is that if you buy a fancy antenna, and need help assembling and climbing on towers, club members love doing this and will not charge. You will probably get a whole crew of volunteers and you only need to serve them a good meal.