That is very similar to how I do a lot of my stuff out of my warehouse, with the exception of having a lot of garage sales (although after this last one, I may try to do one a month through the summer). I do meet up with most of my CL buyers there, and a lot of them end up buying more stuff when they see all the inventory I have.
I think it's a good way for you to get started to see how you like it and see if you can make some money at it, but it would be hard for me to do it in that size of space. Mine is 30' x 60', and it's too small most of the time! I like to buy the 20' and 30' deep storage lockers, so if you were to go out and buy a couple of 10' x 30's, it would be hard to cram all that into a 10' x 20'!
How tall are the ceilings in the unit you are talking about? You could always throw some pallet racking in there and go up. They charge you by the square foot, not the cubic foot, so if you can go up, it's no extra charge! I have racks running down the side of my shop, but they are only 6' tall gorilla type racks. I currently am selling off a bunch of them and am going to get some 12'-14' pallet racks and a small walk behind forklift so I can get the stuff up and off the floor. I figure any furniture I get, I'll put it on a pallet, take a picture of it for CL, and then throw it up on top. Then if somebody comes in to buy it, I'll get it down. In the meantime, it's out of my way! I also plan on taking some pallets and building some 1'-2' sides on them. Then, I'll stack totes or other stuff inside them, mark the front bottom edge of the pallet with what is in there, and put them up on the racks. I've been planning this for a while, based on my reality and how I operate. I do this on a fairly large scale, so this would not work for everyone.