Wait on buying paddles for now
I would not buy paddles until you purchase the boat. Boat width and depth of hull has a big impact on the proper length. it's a question of geometry.
In fact, I would recommend, if possible, to first buy the kayak, PFD's and other safety gear (good quality bilge pump at minimum) and then take them to an area with kayak rentals and see if you can rent paddles in a couple of lengths to see how they work. Or see if friends can lend some to you. Rec boats, especially tandems, can be real barges width-wise, and a shorter person sitting down in a deep, wide boat, can end up bashing the heck out of their knuckles wielding a 220 cm paddle, even a 230. I'm 5' 5" but being long-legged, shortwaisted and short-armed, from a functional paddling perspective I am closer to 5' 3". I normally paddle low volume kayaks with low profile decks that are from 20" to 22" wide and use a 213 cm paddle. But I used to have a 25" wide boat with high gunwales and had to use a 230 to be comfortable. The last time I used a tandem rental I tried several sizes and actually found the 240 was the only size that would allow me to comfortably reach the water without hitting the wider deck in the stern position.
You can get a decent Bending Branches, Harmony, Werner or Aquabound paddle for between $100 and $200 new. At the moment, REI has the Aquabound Stingray for $140, the Harmony Deep Sea on sale for $120 and even the Werner Skagit, which is often part of starter kayak packages and has always been a decent paddle (I have two of them) is only $130. You can even get a carbon fiber Skagit for $180 or an Adventure Technology bent shaft for $185.
http://www.rei.com/gear/feature/search/Google/kayak%20paddle?gclid=CLWUgZ7Cn7YCFQSg4Aod2zsA5g&s_kwcid=TC|13029|kayak%20paddles||S|b|19596106325&ef_id=UNNkNwAAClec-Fkf:20130328132910:s
There are also a number of makers who produce Greenland paddles (my personal favorites) for under $200 -- look on Ebay for a sampling.
I would not count too much on finding a used mid-price paddle. I scan kayak gear want ads almost daily in several geographic areas (friends and relatives have me on alert to find stuff for them) and solitary paddles for sale are rare, except for high-end models. I believe most people keep moderately priced paddles as spares or sell them as a package deal when they get rid of boats. That's how I came by half my paddles.
I have to politely disagree with the contention above that a 220 is "too long" for anyone using a solo kayak under 36" wide. This may be true for the average man, 5' 8" to 6' with normally proportioned arms. But if you have a short upper body and arms, even a high angle stroke and proper rotation doesn't always get the blade in the water from a deep and wide cockpit.
YMMV