Like in life, there is no such thing as Fast money. Well unless you obtain it illegally or in the case of WoW, spend your real cash to buy gold.
My biggest question is, at lvl 47 why do you need 400g? The only thing worth 400g is part of your epic mount price, but you still have 13 levels for that. If your thinking of buying an overpriced epic, please rethink it. You will quickly shard that when you can obtain much much better weaps in instance.
Anyways, as for cash making. All of the profesions equally take time, and making money off of them is hit or miss depending on your server. I would advise picking up a profession you enjoy, because the likelyhood is that if you enjoy it you will spend more time doing it, which in turn equals more money.
Other then professions, there are a few other ways of making cash. Which I am sure have been stated many many many times in these forums.
First off, you can play the AH. I have seen some brilliant buys and sells. But this requires initial investment case, and a smart brain to figure out if you can buy and sell and make a profit. Some ppl excel at this, others...do not.
Secondly, run instances. This brings in 2 kinds of revenue. First the cash from drops. Or if you choose to run lowbies, you can offer a "rush" fee for many of the lowbie instance. Depending on your capabilities, you could rush a group through VC fairly easily and charge a small surcharge for the run. At level 60 my hunter gets about 10-15g per run for SM and Gnomer and about 5g for VC, SFK. I have done other runs, and base my rate mainly on where I am going and how who the group is. Hell I have even been paid to run LBRS with my priest.
Lastly, just farm. Humanoids tend to be a good choice for the cash they drop, and cloth sells fairly well. Farming SM Graveyard is especially lucrative in my experience. If your a skinner, farm beasts. Simple as that.