There are many bikes on sales in this forum. Some are from direct owners and some are from bikeshops.
I would like to caution about buying from direct owners. Some of the questions you should think about are
1) Owner has changed a lot of parts on the bike, added accesssories etc. Some even overhauled the engine and claim that bike is in good condtion. Think about it! Why would anyone in the world spend money to repair the bike, then sell it off to you?
2) All bikes have wear and tear items. The older the bike, the more problematic it is. Yet there are sellers claiming that the bike is in prefect condtion. How is that possible? Even new bikes are not prefect.
3) Assuming you find a really good offer. Seller dilligently maintain bike. Outlook is good. Wear and tear parts replaced and there are receipts to prove. You want to buy from him/her. Please think again. Outlook can be done nicely. Parts can be replaced by a good seller. One word of caution though....Internal leaks within the engine that cannot be seen by the naked eye.
For example, if the bike has excessive oil consumption problem, you will not know it till you have clocked up some mileage. By the time you know, it is too late. How about coolant seeping into the combustion chamber slowly? It will be months later before the bike will give out smoke. Do you have recourse? Anwer is NO.
Therefore, please buy with care and ride safe.