Buying selling cards

Is it possible to buy sell and trade cards as a hobby for extra money? I want to buy all the random holo cards going around on eBay for cheap and buy lots of random cards in bulk and go through and sell the valuable cards individually and take some of the holos and put them together with basic cards for an auction on eBay and sell the 1 card with 10 random shitty ones so they make money.

I once found an auction for 2 cards that were holo and the auction went for like 7 bucks and one of the cards alone was selling for double that so I regret not buying. I also collect them as a hobby so just collecting and sitting on them doesn't really bother me either if they don't sell crazy high. I'm hoping to add to my collection while doing this.