For your first question, just get albums you like, i've gotten copies of Jon Anderson albums that I really like, and various others. Vinyl quality is superior, so I like to hear my favorite albums in their true glory.
For your second question, they certainly are collectible, but I wouldn't buy them expecting to make a living off their sales. They only cost around a dollar or so depending on the quality of the record. Some cost up to 30 to 40 bucks, but those are mint condition, mostly.
When you're purchasing vinyl, you want to focus on the quality of the sleeve, like if it has the plastic wrap or if it's bent, etc. A perfect vinyl quality would be unopened and the plastic wrap completely perfect. Here's a list to further assist you with the quality of the record itself as well:
Vinyl Grading and Condition Rating System - VINYL LP Album Cover Museum
My and my girlfriends collection is a little over 200, it's a lot of fun.