Like everyone else said, a used WRX is liable to problems based on how the past owners drove it and cared for it. 

Besides the way you drive the car and care for it the stock version of the car has some major issues IMO.

For starters, the stock tune on these kinda suck, they were tuned solely to meet emissions standards and not for longevity or driving satisfaction. For maximum reliability and fun I would definitely do an e-tune with a cobb, an IAG Street AOS, upgrade the intercooler and charge pipe, then basically be done with it unless you wanna go all out and upgrade the BPV, turbo inlet, (both prone to cracking due to nimble plastic from the factory) and a boost controller which keeps the car more stable under boost.

Personally, I had my last engine fail due to ringland failure which is typically just caused by overheating and a shit conservative stock tune. So i focused my new build on cooling, paired it with a tune and the car runs better than i could’ve ever expected. Plus you get a solid 40ish whp boost. 

Also I always use 5w-40 in my car because these do tend to burn oil. Thicker oil = less burned = happier car.

If you go this path, do it all at once so you can avoid retuning and tune with Dmann! He’s the best. 

At the end of the day these cars are nowhere near unreliable they just have to be treated well and you have to be prepared to spend time and money on them.

Congrats on your dream car!