Yep I have an older F150 XL pickup. It is harsh on gas consumption and with towing the trailer that will get quite a bit worse but the savings can be substantial in the long run I suppose (as opposed to living in an apartment/house)
I live in Canada and would like something that is easier for 4 season usage. I can make do with warm clothes and down blankets etc but for example while working on my laptop in the winter, it will be easier without gloves ;-)
I can do without buying new but I am not too mechanically handy and do not want to spend a lot of money paying someone else to fix any issues with older trailers. However, I would definitely be down for buying something older if it is in good shape.
Arctic Fox is among the best known four-season RVs. I don't know of any other manufacturers who specialize in that area off-hand. Modern RVs are better insulated than older RVs, in the general case, especially when comparing similar quality levels (e.g. a new Airstream or Winnebago will be better insulated and energy efficient than a similar model made 25 years ago...but, 10 year old models are probably comparable to current models, and will often be obtainable for 1/3 the price).
With a travel trailer, there's much less concern about needing to be handy than there would be a with a motorhome. While things are going to break, and things are going to need work, that's true of new or old RVs. My motorhome (which was 7 years old when I bought it) constantly needed minor repairs. Likewise, my 32 year old Avion also constantly needs minor repairs (and it needed and still needs some major repairs).
Sticking with ~10 year old trailers is probably the right time frame for someone who has no desire to have a fixer-upper (I don't recommend fixer-uppers, no matter what, as they always cost more in the end). But, if you start searching well before you want to leave, you can be extremely picky and you'll find someone that has loved their trailer, and kept it in great condition. A lot of trailers only see seasonal use...so they've only been lived in for maybe 6 months, even if they're 10 years old. If the owners winterized them properly, and kept them covered or at least protected from direct sun and such, a ten year old unit can be damned close to new. Higher quality trailers hold up better to aging than cheaper ones, so look for the high end brands (there's too many of those to list, but if you spend a few weeks checking out RV dealers, and RV shows and reading some forums, you'll get a feel for the ones that people really like).
I'd recommend you spend some time learning about them. There are definitely quality differences; usually you get what you pay for, though buying older can get you a great deal, comparatively speaking. I would much prefer a high quality old rig to a cheap newer rig. But, older rigs can have a lot of hidden problems; my Avion has had a much rougher life and needs a lot more work than previous owner disclosed (for a variety of reasons I bought it knowing it needed work but some of the work it needed/needs is beyond what I expected or could reasonably find in the brief inspection I gave it).
One probably can't easily summarize everything one should know before buying an RV, but I'd recommend you start reading up on them now, and don't plan to buy for at least a month or more. Go visit RV dealers (with no intention to buy new, or even to buy from a dealer at all, as they will overcharge by a huge amount in the majority of cases...it's normal to pay half what a dealer would charge for a used RV).
Do you already have a tow vehicle? That's probably where you need to start, if you plan to go the travel trailer route. If you plan to live in the trailer full-time, you probably need a big truck to haul it; I've got a diesel F250, and it works great. With a weight distribution hitch it'll comfortably haul more than my house (which is probably about 9000 pounds loaded with tanks full).
As the other commenter recommended, road side service from Good Sam is a great idea; I've used both Good Sam and AAA, and Good Sam does a slightly better job getting the right sized tow truck out to you when you need it.