It is possible to pay other people to unlock your storage. You must temporarily give them Maintenance and Housing Storage permissions (Character Panel --> House --> Permissions). Before doing this, you might want to take out valuable items from storage (I did not bother and had no problems).
I have had the best luck advertising in the low-level free zones, rather than global channels. Global channels are frequented by high-level characters whose comments inflate the price. Make sure to mention that Mithril Coins may be bought in the Store, otherwise new players may think they cannot buy your gold. For reference, I paid 500-800g per unlock, but I do not know if this will turn out to be too high or too low in the long-run, as it only encompasses 16 transactions and does not include all servers.
On the flip side, if you are looking to buy gold (legally), advertise on your server's global channel.
When selling gold, I suggest making sure that any potential buyer properly understands the TP conversion ratios and what it will ultimately cost them. I just received this:
hi! that TP was $80 worth which I miscalculated earlier, so would you like to pay me more so that I don't feel cheated? I hope that wouldn't be a big problem for you
I mean you have a kin, and it wouldn't be much money for folks if some high leveled toons donated some
it's hard to explain how I miscalculated, I just made a blunder calculating TP
TP into $$
and it's going to be perfectly free will for you and your kin, I'm not gonna insist or blackmail or whatnot.