To echo / expand upon what everyone else is saying...
Snowmobiles aren't like seadoos, in the sense that there has been incredible progression in technology. A modern seadoo is bigger and has a bit more power, and XP / GTX likely burn oil, but otherwise they're the same. They start, they go forward, they might even have reverse, they float on the water. When it's rough out, you get wet. Etc. Lots of nifty tricks (the "brake" system, etc), a bigger more muscular thing...but they're the same.
A modern snowmobile is so fundamentally different from a mid 90's that they're almost not the same vehicle. The seating and riding position is completely different, the engine and chassis are completely different, the suspension is completely different, and all of those things matter. Here's a quick history,ish:
~96-2000: S chassis. Old rotary valve engines are relatively bullet proof. They go pretty good in a smooth straight line, not so great elsewhere. Almost no suspension, chug gas and oil like it's going out of style, getting much harder to find parts. Critically, your legs stick straight out in front of you, with your ass on the rear of the sled. Exceptionally uncomfortable on anything but the smoothest trails, and makes handling and stability less than ideal. My first sled was a '99 and I loved it dearly, so don't get me wrong, you can still have a ton of fun if you want to dip your toe in the water. But if you even remotely like the sport, you'll want to upgrade soon. Should be able to find them for <$2k each, even with covid pricing.
99-'03: ZX Chassis. Like above, only slightly better. A bit more comfortable, a bit more suspension, slight improvements in handling, a little easier to fix up. Legs still stick straight out in front of you. The best "sit down" (read:ancient) snowmobile ever made. Should be able to find them in your budget, but will leave less money for repairs / upgrades that are inevitably needed on something of this age.
'03-'07: Rev chassis. Quite literally changed the sport forever, because you no longer sit on the rear with legs in front. Do some googling - you'll learn lots. The engines and suspensions are almost identical to the ZX (with minor improvements in later years, that are probably out of your price range), but the fact that you ride it like a bike instead of a lazy boy made that somewhat irrelevant. Still very old and uncomfortable and outdated by today's standards, but a massive improvement. Unfortunately, finding two in good condition is likely out of your budget. Crappy ones, maybe.
'08-'12: XP chassis. Took everything the Rev did, and did it miles better. Your knees aren't cramped, the suspension improved again, the engines improved dramatically. This chassis is the oldest you can go while still being on a "modern" sled that, in most cases, is at least in the same league as something brand new. Lots of rentals will be an XP as they made the budget version right up until a year or two ago. You'd be happy on these for a long time, and can likely get at least one in good condition for your budget (but not two).
'13-'17: XS Chassis. Like the XP, but with tweaks. Mostly just plastic, but Rmotion (the rear suspension that is literally magical) became the standard on this chassis, and is still the standard today. Any XS sled is fantastic, and unless you're die hard passionate, there's no need to upgrade. Until quite recently they were the latest and greatest. I owned an XP and an XS and while the chassis is nearly identical, the engine, plastics, suspension, etc made it feel like a whole new sled that really was "worth it". Likely out of your current budget, even for just 1.
'17- now: G4. The latest and greatest, and oh baby are they great!
