This should be fun. Please reference "L" for Legends and "S" for Select.

Varies upon age and rarity. L's retail is under $20 while S's goes for about $25.

S has more focus on detail, while L focuses on articulation.

Varies. Retail stores, local comic book stores, online, etc.

Depends on what you want. L figures are pretty common for going on sale but those are the ones which no one wants to initially purchase.

S is my favorite. I prefer to not have to really pose something as I'm just not creative in that sense. The figures are nice to look at.

L is a superior choice if you want figures to play with. Some people collect them seriously though so I wouldn't bash them as "kid's toys".

Depends on how many hands you have I guess. Or if you want to pose "battles".

Check the source. Sounds sketchy to me though. I've made the mistake of ordering fake figures because they were lower prices. It's better to pay a little more and actually get what you're expecting.

Also something to keep in mind if you don't really know characters: people sometimes swap out an L figure with another random figure and return it. It's a sick way of getting figures for free.