After owning a 2000 Legacy L wagon for 7 years so far, I don't regret it. However I wouldn't do it again due to all the age-related maintenance.
Your daughter has a 1995 model so I suppose you both have an idea of what you're getting into? I love my 2000, still own it, but sooo much damn maintenance and parts failures. If you're a young mechanic then maybe, but be prepared to do unscheduled maintenance on the regular. If and when I get a new car it will be another Subaru, but I'll be looking in the 5-10 year age range.
From 15 years on you get a lot of components that start to go bad. Starter, alternator, fuel pump, starter relay, fuel pump relay, both oxygen sensors, the catalytic converter, hydraulic clutch cylinders, several different suspension bushings and the water pump have all gone out on me. The timing belt is rubber and a regular maintenance item too which you will need to either be certain when it was changed or change it right away. I've also changed out countless small things like the turn signal indicator, the control for the driver side windows, the hydraulic shocks for the rear hatch, rotten rubber hoses and many other small things. I've also had to do age related things like restore the headlights and nuke the cabin air ducts with fungicidal spray to clear out the mildew smell.
On top of all these age related mechanical issues you have the age related cosmetic and interior issues. The foam in the seats ages and starts to crumble in some areas, and the paint is cracking like alligator skin. Sure nothing particular to a Subaru but why deal with all that when you can just buy a newer car? Any extra you save on the price will be lost paying for unscheduled, age-related maintenance costs. If you're paying a retail mechanic for maintenance then forget about it - older will be more expensive over time. I can't even imagine how broke I'd be if I couldn't work on this car myself.
I'm in California where there's also no real salt or rust to deal with, so my Subaru was in relatively good condition to start. I made the mistake of trusting the last owner who said he recently changed the timing belt, which snapped. Not the car's fault but I did replace the valves clutch and head gasket in a major job during first year of ownership. I also replaced the struts twice, once when they went bad and a second time with Outback struts for the height gain. Legacies are low to the ground and will scrape a lot of stuff if you live in an area with uneven terrain, potentially causing additional damage and maintenance (scraping busted my cat).
Did the clutch again because a standard grade clutch wasn't strong enough (Exedy 15801 proved an excellent upgrade). Did the head gaskets again because a combination of poorer quality non-OEM gaskets during the first job and not changing the coolant soon enough rusted them out. Coolant also protects the cooling system from rusting until it gets too old (2 year change interval). If you notice your coolant turning red, it's probably from your MLS head gaskets rusting away. It's what happened to me and I'm pretty sure this is a major source of the infamous Subaru head gasket blowouts. Very religious about my timing belt and coolant change intervals now!
The car is great when it doesn't break down, which is reasonably infrequent - perhaps once a year on average. It did also teach me a lot about working on vehicles. I'd recommend it as a starter car for a mechanically inclined teenager or college student, or anyone on a limited budget with free time on their hands, or as a backup or project car. Your 21 year old daughter might find it a nice upgrade if there's someone in the family who can help out with maintenance. The handling and extra bit of engine power would be a definite upgrade over an earlier EJ22 Legacy.
But if you can afford it then consider a newer model Subaru. The components will last longer. A lot of stuff goes bad after a car gets past 15 years old. If you're going to buy one of these older Subarus and aren't in a hurry to make a purchase, then I'd try to buy one that's already broken down or on auction for cheap. 2K is what I paid in 2014 for my 2000 Legacy. It didn't have a leaking headgasket either, but I guess that' s the cost of inflation these days? I don't know about external leaks; mine was an internal one between coolant jacket and cylinder, so lots of white smoke. As an aside, it is possible to replace the headgaskets without removing or even unbolting the engine, it's just an awkward angle that's rough on the back.
At least be ready to invest in maintenance because it will need it soon enough.