yeah, you can use the house merchant in one of two ways.
The first way, which I use, is to just not withdraw the money from items I sell on my merchant...I usually have 20-100 plat stored on my consignment merchant and I just let any of my toons withdraw it as they need. You do this with the /settle # (where the # is the amount of copper you want to withdraw so 10,000,000 is 1 plat)
The other way is what coldinside said is really the same thing, but he just is saying if you have no money from other people buying things off your CM, then just place a dummy item (can be any useless item you might have) on your CM and have the toon with the extra cash buy it off the CM (lets say you place a level 10 item for 10 plat b/c you want to give one of your toons 10 plat)...they buy it for 10 plat..the money is now on your CM...you log onto your poorer toon and /settle the money out of the CM...takes a few minutes of time, but not hard to do.