One of the biggest expense items for most folks, Bike racks (to carry your bike on a car) can be found used on Craigslist and eBay, as can most other items. What kind of gear are you thinking of? (commuting, road, mountain?)
I bought shoes and pedals on Craigslist. &200 carbon specialized and entry level LOOK for $100. I just washed the shoes. No issues. About the only thing I wouldn't buy used is shorts, unless I knew the person.
I've bought most of my clothing-as well as panniers, bags, racks and other accessories via my local Craigslist and online classifieds. All have been gently-used and were great deals. The high cost of cycling jerseys in particular has been daunting. It finally dawned on me that a basic wicking shirt is all I really need for the job.
You might also want to to try your local Freecycle chapter or yard sales. It's not unusual for people try cycling briefly, then decide it's not the right activity for them-which results in garages filled with bicycles and/or accessories that were only ridden around the block.
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