BEGINNER SURFER! NEED HELP!

So just recently I've picked up surfing and almost immediately I've fallen in love. Although barely able to stand on a board, I'm looking to invest into my own board now. (I've been borrowing a friends) Since I'm just a beginner, I'd like to buy a second hand board. I found a few on craigslist, but I'm still afraid of being scammed and buying a complete dud. Any advice on how to pick a board? I'm also going to leave a few links to the boards that I'm interested in and hopefully from the photos below you guys could help determine whether or not they're okay to buy? And by okay to buy I don't mean whether or not that board is right for me, but instead whether or not that board is in good condition, about to break, or has sketchy looking repairs. Thanks!
Along with that... I still don't fully understand what exactly the differences in a surfboard mean. Epoxy vs PU? Shortboard vs Longboard? What do fins do? I live in LA, so I was wondering if a Spring suit that's 2MM should be okay?
Surfboard Links:
http://losangeles.craigslist.org/wst/sp ... 75720.html
http://losangeles.craigslist.org/wst/sp ... 46454.html
http://losangeles.craigslist.org/wst/sp ... 01128.html
Along with that... I still don't fully understand what exactly the differences in a surfboard mean. Epoxy vs PU? Shortboard vs Longboard? What do fins do? I live in LA, so I was wondering if a Spring suit that's 2MM should be okay?
Surfboard Links:
http://losangeles.craigslist.org/wst/sp ... 75720.html
http://losangeles.craigslist.org/wst/sp ... 46454.html
http://losangeles.craigslist.org/wst/sp ... 01128.html