Nothing wrong with buying used as long as it's a name brand. Beware of the semi-recent flood of imported stuff sold at prices so low it seems too good to be true.
An example of what I mean:
http://www.alibaba.com/product-gs/200566966/best_two_stroke_1000w_generator.html
Models like that can be found
new in the $150 to $175 price range. You'll also find models like that in dumpsters everywhere after several hours of use.
And I need to know too.....stay
away from Honda or Briggs? Huh? What????
Check your local Craigslist and garage sale ads. Have the seller demo it for you. And if you find a sweet deal on one that doesn't work, send it to me and I'll fix it.
For use on something non-critical like tire warmers or power tools, you don't need anything fancy. If you'll use it occasionally during power outages to run your late model electronically controlled furnace to keep the house cozy, then you want to step up to a model with better voltage regulation. Before I bought one of my own, I borrowed a family member's to run my furnace during a storm. I fired it up and with the engine running at a dead-steady speed, the output fluctuated between 95-135 volts. Electronic stuff no likey gensets like that.....