Auction house is not a safe way to transfer gold. The safest way I've seen is guild bank transfers but I haven't seen any websites offering this so the next safest way is face to face transfer. Make 100% sure that the company you buy from offers face to face transfer. Also see if you can get them to trade the gold incrementally, and put something in the trade box when you accept gold (can be as little as netherweave cloth.) Finally I strongly suggest receiving the gold on your 70, not a level 1 bank toon.
All that said, blizz usually bans the person supplying the gold not the person receiving the gold, but it has happened so be careful. /forums/images/%%GRAEMLIN_URL%%/smile.gif