I think t360 is right on with his answers. I'd like to add a thought to what he said about question 2 though.
Unless you have a LOT of money to put into your collection, you should look at collecting stamps as a rewarding and fulfilling hobby - not as an investment. Only a tiny fraction of the stamps collected have appreciated in value over the last decade or two, and many, if not most, have actually lost value given inflation.
You can buy a year's worth of fun for $100 or less by buying large lots of used stamps for little money on
ebay or elsewhere. Buy a few lots and learn about the history and meaning of the stamp topic - then when you hit the Powerball you can start investing!
Have fun and share your enthusiasm with another person!