Buying a used iphone 3gs online - are all the unlocked ones jailbroken, too?

Question

Hey there :-)
My iphone was stolen recently, and as I wasn't banking on having to replace it until about a year later, the replacement will need to be a used one so I don't totally blow my budget I looked locally but there's nothing interesting, so my only choice is probably going online, specifically ebay.
Now, the issue is, I need one that's unlocked, because I won't be using it in the same country it's bought (and the odds of finding a phone locked to the specific network are slim to none). But I keep finding iphones that are marked 'unlocked and JAILBROKEN'. Trouble is, I'm not sure I want a jailbroken phone, because I've heard jailbreaking ends up causing all sorts of problems with the software, and I don't need that: I see absolutely zero benefit in sacrificing any of the reliability I've come to know and love just for the opportunity to download a bunch of potentially lower-quality apps, many of them games which I don't use anyway - not when there's so many interesting apps I can get without bending/breaking the rules (not judging those who do this, just explaining my own perspective, how it works for the kind of use I make of this).
But most of the phones listed as 'unlocked' also have 'jailbroken' in the description. So now I'm beginning to worry that these two go hand-in-hand - like maybe, jailbreaking is a first step or something for unlocking the iphone, so that by definitiion, an unlocked iphone is also a jailbroken one. Is that the case?
And if so, what should I pay attention to when buying so that I can minimize the chance of getting a dud? If not, can I ask one of these sellers to undo the jailbreaking somehow and just send the phone unlocked only - is that a possibility? I'm reasonably experienced buying on ebay (studying feedback, etc) but this is the first large purchase of this kind, so ANY advice you can think of for this will be very very welcome indeed

Answer 1

Dave Sawyer -
yes, unfortunately a new iPhone is completely beyond my means right now. I tried to figure it out but the money just isn't there for that kind of purchase It doesn't help that iPhones are priced at a high premium where I am - it took me a few months to save up for the one that was stolen! and worse, older model iphones don't get discounted more than a couple dozen euros at most here, and even when you can find demonstration devices, you'll be lucky to get 5% off a device that is a complete mess.
Okay, enough wingeing I really want to thank you for the detailed post - I can honestly say you saved me a lot of grief because other advice I received was that I could buy a JB iphone and then get rid of the JB with a simple restore! Which sounds like it's definitely not the case.
What you said confirms the wisdom of my decision to stay away from JB iPhones. They honestly sound like they are better suited to people who just like to tinker with their device, and if the tinkering interferes with the phone's reliability, that's not a big issue to them because it's used more as a toy or educational aid than a fully fledged tool, as it is for me.
I have found a few listings for 'factory unlocked' iphones. What do you think of these? Are they legitimate? One of them seems to be from a larger business seller who sells only this type of thing, and the others are original owners (who bought them from the carrier or Apple) selling their own used phones.