1) if accumulating btc is the end goal, does it matter which coin I mine since I will just sell anyways to buy more btc?
Yes of course. According to the hardware you get (type of gpus I assume) there's better coins to mine with each. For example if you get amd cards you mine ether. If nividia --> zcash.
2) which coin is easiest to mine (roi I guess)
Head over to
whattomine.com and type in the number of cards you plan to buy and you should get an idea.
3) if I have a room that can be dedicated to mining, Can I just buy some fans to help keep it cool?
Short answer yes. Long answer search the forum.
4) which setup is best for mining ethereum type coins and which setup for script based coins? I have about a $5000 budget (going slightly over is ok)
RX 580 cards. Search for ethereum mining rig.
5) if I buy a nice rig/setup, how long until it’s obsolete? Or is it just a matter of replacing the cards if they burn out?
It's arguable but should be not less than 2 years for a card to die.