What is your idea of a used RWS 350 Magnum? This one is painted in camo all over from the tip of the barrel to the end of butt stock. It slipped me whether it was a .177 or .22 cal.

When buying a used air rifle what do you look for? I saw an article where someone had some seal worn out in his air rifle and had to get that replaced and possibly tune. Some folks seem to think paying $300 for a top-flight tune is worth it. But if I was buying used air rifle and figured in the cost to tune a rifle at a mid-price tuner...what would you pay the cost for this 350 Magnum?

Any tip on how to evaluate an air rifle? I saw on Arizona website that they have RWS pellets. Are pellets specific to each air gun? I may have to order some pellets and see if I can shoot this air rifle to ensure it at least works.

Do you have any experience shooting "springer" airguns?

If not, hold it, but do not "grip" the forearm. Consistent hold is important. Hard to explain, youtube is your friend here.

Are you buying this in a FTF sale or over the internet?

Over the net or any non FTF sale would require a 3 day return agreement if it were me and I would shoot/test it quite a few times with several different pellets.
If you have a scope on it then shoot at least 25 yards and hopefully some 50 yard shooting.

As I remember the specs this is NOT a toy and will send a pellet a long ways.

My guns are far less powerful than the 350 and I can hear a pellet zing off into the distance from a ricochet occasionally.

Considering you can buy a new RWS 350 Feuerkraft for $360, and occasionally on sale for $299, I personally wouldn't pay much over $200 for a used spray painted one. RWS 350
Pellets are just like ammo, each gun has its own preference. Several places sell "samplers" so you can try a few of several different brands without buying a whole tin of each.
Tuning can help smooth out the firing cycle of your air gun and make it easier to shoot accurately, but to my way of thinking I would rather put that money into buying a higher quality gun to begin with that doesn't need a tune to shoot well.

Most inspection periods say "no firing". You can damage a spring powered gun by dry firing it. I've sold used air rifles with an inspection period, but I didn't want the buyer firing them unless I was standing there watching.

I'd be cautious of the spray painted stock if it's the wood stocked model. I've seen guys break a stock, glue it back together, then give it a shot of camo paint to hide the break.

I agree with tmitch that you'll just have to try a few different pellets to find what your rifle likes.

I've owned a 350 in 177 and 22. In my opinion the 177 versions are shooting too fast. The lighter pellets will have a sonic crack. The 22 version makes a super high powered hunting airgun.

This 350 I saw at a gun shop was listed with a tag of $99. Pretty cheap for a springer. But I have seen post on some who have had their springers "tuned" for $300. To my way of thinking...it is best to buy a springer for around $300 and be ahead of the game. The camo job looked decent but honestly who needs a camo job on a springer. And since this is a magnum version...I have rimfires for those shots that need more whack. I doubt I cn shoot springers in my yard in the summer time when my neighbors have their windows down. But I learned something...you can damage a spring powered gun if you dry fire it.

99 bucks . . .
Either they don't know airguns, something is wrong with it, or it is a deal.

I would still want the privilege of shooting it before the deal is FINAL.

If you have any mechanical aptitude, it's really easy to replace the spring and seals on a springer. So long as the bore of the chamber isn't scored and the barrel isn't damaged, I don't see how you could go wrong for $99.