That is a steal for that price!!!!!! Don't need to do much to that ride!!!!! If I had some extra cash I would drive out and pick that baby up!!!! 
That is a steal for that price!!!!!!This bike may be steal for the price, but who's doing the stealing?
It would be a burn for the buyer if the engine is going South because the air filter is defective. You get what you pay for in life, so buyer beware. Deals ARE out there to be had, but I sure would check it out to make sure it's mechanically sound. Nothing against the owner of this bike because I don't personally know him, but I have seen what a Proton can do to an engine.
Too bad it has a Proton on it.
From what I've seen of defective machining on one Proton filter housing and their filter area design............I'd never buy a bike that ever had one on it. The only Proton I've internally inspected leaked air so badly around the sealing surface, it caused the engine to fry. Internal engine damage had occurred before the owner detected there was a problem. This particular Proton has a machining flaw in the sealing area of the housing where the filter element seats so as not to clamp and seal the filter element adequately. It is possible this filter housing was a fluke and the only one machined incorrectly, but if I owned a Proton, I sure would inspect the filter pocket seating area for correct sealing. A good way to check a filters sealing properties is to wet the downstream inside surfaces of the filter housing with heavy oil to catch any debris that may be getting by the filter. Take a long ride over a few hundred miles and then remove element and inspect the housing for debris. Due to the flat design of the element (and a potentially loosely clamped/fitting element), it has a tendency to distort and lift off the sealing surfaces when it becomes extremely clogged.
Besides having a tendency to leak raw air into the engine if the filter pocket was machined wrong, the designed filtration area of the filter is too small for the engine size IMHO. There is little or no safety factor designed into the CFM rating. Typical air filters for internal combustion engines are designed with a CFM rating with a safety factor of 2-3 times the actual CFM requirement of the engine at a specific pressure drop across the filter. This filter is undersized for the application IMHO. While a freshly cleaned Proton filter will allow the engine to operate without problems when clean, it doesn't have the additional surface area to maintain a free flowing air cleaner for very long before trouble could developed. After seeing the Proton I inspected, if I had one on my bike, I would inspect the Proton filter pocket to insure it is machined correctly and not leaking. Owners need to check the filter often to see if/when the filter becomes so plugged with debris, the sealing surface begins to get compromised and allows raw unfiltered air into the engine. Unless the owners does this, the engine could suffer damage before the owner detects a performance problem. Internal damage will occur before performance begins to suffer, if the filter leaks raw air passed the sealing surfaces. Yes this could happen with any filter, my point is due to the lack of safety factor built in to the designed filter area of the Proton, this can happen with the Proton faster than an adequately sized filter.
I’m not saying every Proton leaks air, but they should be checked to make sure they don’t and I sure would preform a compression test on this bike if I were considering it.
As I've said previously, I don't know the owner of this bike and I'm not trying sabotage the sale of his bike.
Just my two cents and comments on facts I've seen with one Proton filter in an effort to help other Proton owners avoid a costly engine rebuild................like my friend went through.
PS........
In retrospect and fairness to the original poster............My comments about Protons may have negative conitations for the seller of this bike, so I'm asking moderators to move my post to a more appropriate forum section.
Thanks
If this gets moved.........The new post subject line should read.............
Protons.............They SUCK! 
