Now, if you want to fly fast at 70, you will need between 4,000 to 5,000 gold (depending on your reputation).
That is a lot of gold, but it is, in fact, pretty easy to make if you follow this five advice (take it from someone whose character all had epic flying at 70 and 310% at 80).
1) If you haven’t done it yet, do it: Make a brand-new character that will live next to the Auction House and will be your banker. Your Other characters can gather loot then will mail it to this alt, who will take care of business. You will gain time and hereby, gold, because nowadays, time is gold!
2) If you have more than one character, you are playing, have at least one who has only gathering professions and let him/her farm. Farm for some hours and send everything to your banker.
3) Starting at level 70 you can do various Daily Quests. Each of these pay a decent amount of gold and you will acquire some sellable loot. More dailies are coming at level 80, 85 and 90, of course. In a few hours, you can make hundreds of gold.
4) Use an add-on like Auctioneer or Auctionator and pay attention to what things sell for on the Auction House. Don’t overprice (you just won’t sell it) and don’t undercut too much (no need to cash 50 gold, when you can cash 100).
5) Sometimes, when completing a quest, there will be several quest rewards to choose from, but no one is usable for you. Hover over each item and the tooltip will tell you what it sells for at the vendor. Pick the one that sells for the most, then vendor it. Sometimes there can be up to 20 gold of difference between the cheapest and the most expensive.