No, this isn't about how you can literally buy a raid slot, much like Gevlon did many months ago. This is more about how to spend your money to get great gear. It may seem a little obvious, but it's a lot easier to learn how to make money on the auction house and then buy epics than to run hundreds of heroic dungeons to get geared up. Ideally you should be doing both but making money will dramatically reduce the amount of time you spend in the dungeon finder queue. I recently (with a lot of help questing from my wife) leveled a hunter alt to 80. A mere 3 days after I hit 80, most of my gear was at least an iLvL 200 epic. There's a ton of great crafted gear out there for new 80's to buy. Before I even hit 80, I had the Crusader's Dragonscale chest and wrists for a total of around 6k gold and those are iLvL 245 pieces. Just spend a few days shopping around and eventually you can get a good deal on enough epics to get you into ToC 10 man raids.
On a related note, I recently came into possession of Rowan's Rifle of Silver Bullets, which is a tanking gun that drops off of trash in Icecrown raids. I was reluctant to take it at first, because other than Hit, it has NO hunter dps stats. But, one of the hunters in the raid made a very good point. He suggested I take it anyway and use a hunter dps spread sheet, like the one from http://www.femaledwarf.com/ to see if it would be an upgrade. So, I did and I was shocked. My hunter had been using the True-Aim Long Rifle from ToC 5 non-heroic. It's a good starter hunter weapon and better yet, it's a gun and no self respecting dwarf would be caught dead with a bow. I plugged the Rowan's Rifle into the spreadsheet and found that it was a 311 dps increase! I then wanted to compare it to other ranged weapons and found that it was higher dps than the iLvL 232 crossbow that drops off of Ick in Pit of Saron heroic. Compared against the BRK-1000, Rowan's Rifle is only 11 dps lower (unbuffed).
So, for all you fresh level 80 hunters, if you can find a good deal on Rowan's Rifle, pick it up and you'll be using it for a long time. Just be prepared to defend yourself if someone inspects you and sees you using a gun with tanking stats. Better yet, prove them wrong by showing them your dps in Recount.