If any bike has over 3k miles, the 3 easiest ways of determining maintenance is by looking at the chain, brake fluid and coolant. If the chain is clean, lubbed and adjusted properly. Second would be brake fluid color. Third, coolant level and color. If those three items pass the test, than you know the person knows a little more about bike maintenance than just waxing the bike and changing the oil. I think we can agree that most sportbikes are bought by younger people. Younger people tend to be harder on riding the bike and maintenance neglect. If there are any signs of cages, 12 oclock bars, over sized rear sprocket or any other signs of stunting. My preference would be to move on to another bike.
Many things to look at, thought I'd help you with a couple of the most important. When talking to current owner seldom their words mean nothing. You need to learn to decipher how a bike has been treated by learning maintenance yourself and knowing what to look for. If a bike has under that mileage, I'd worry very little how the bike was maintained. Other than maintaining and treating it properly from that point on. It's also a big deal to me, to know that the bike was kept indoors or not. I'd also bring a wrench to take a look at a plug and air filter. But, that's just me. On a used bike, I also like to see wide chicken strips. Then I know it wasn't ridden very hard per say. Check for burnt rubber under the tail for burn outs, etc. Leaks in fork seals. Play or slop in the steering head bearings. The later would be signs of stunting or simple neglect to have seals or bearings replaced. Easy to check the pads too.
