My advice is have a cheaper holiday this year, or perhaps do some overtime at work for a bit and put the extra cash into buying a band new bike.
I have had low milage, good clean used bikes some years ago. There is still no way of telling how much it will still cost to make a used bike good.
Here's an example :
The last secondhand bike I bought was a 500 miles 6 month old, never trail ridden, as new WR250.
I found out after scratching my head for weeks, why I couldn't ride it very well. It turned out the previous owner was short in the leg and thought it would help if he let half the gas out of the rear shocker. He then removed, all but 20ml of the front fork oil in an effort to also lower the bike. What a moron !
I sorted the bike out once I had spent hours pondering and adjusting. It just shows you that no matter what you do, or how careful you are when buying secondhand, the fact that a complete plonker could have messed around with it, made a new bike purchase my policy thereafter.
I have bought a new bike almost every year since. I now ride my bike in my spare time, I don't spend my spare time repairing it. I never really need to replace or repair anything except tyres, oil and chain lube.
If you do buy secondhand, just remember this post, and the fact I told you so.
Ride it or repair it.. It's your choice.