Complete lasers over 5mW are illegal to sell (import) in the US. Most of the "5mW" ones on eBay are way over spec. Most of my eBay greens output 25-47mW, all were sold as "5mW"
Look around here (use the search) there are plenty of posts and info on eBay lasers.
Also some names of eBay sellers who sell overspec lasers.
As far as use, unless you have an FDA wavier, and FAA approval, you can not even shine a laser over 5mW into the sky.
Does this mean you will get busted if you do? NO!
As long as you use common sense and don't shine them into the sky when there is a plane anywhere that can be seen or heard.
Or start shining them through your neighbor's windows or at cars, etc.
A high powered laser can be seen for miles.
I had a friend drive to a tower 1-1/2 miles away and see if he could spot my 50mW 532nm.
He said, "it was so bright that even if he was not looking in that direction, it would have caught his attention".
And that was only a 50mW (67mW true)
Order a few from different sellers on eBay and you will almost be guaranteed to get a "hot" one. (most of my greens that I was talking about, I paid .01 to .99 cents for)