Make sure you look at the hydro test date before you buy. Tanks must be tested every 5 years. If the test date has expired factor in having to spend an additional $25-30 for the hydro test you will need before you can get it filled (factor in this cost too). Before buying a tank it is always wise to figure out where you will get it filled. Some places fill, some will only swap and some will only swap if the tank was purchased from them.
I got my 10 lb tank at a fire extinguisher shop, refurbished steel (cleaned up and freshly painted), tested and filled for a total of $60. Prices vary a lot so do your homework before you decide that a CL buy is a good deal.