I would suspect a blown cross over pipe, car overheated and blown head gasket. These LR4s dont sell for much so I would just find a better one. I saw a 2015 with 60k miles listed for 15k the other day. It's crazy value when a 4runner with 100k+ miles will sell for over 30k.

There are a couple things to watch out for but they will last a while if you know what you are doing.

- cross over pipe is the biggest issue. I would suspect that car had slow leak, the owner got use to filling it up every other month, then one day it blew up on the highway and he/she thought they could make it to the gas station. instead they cooked the engine and blew the head gasket. thats how most of the 2014+ SCV6 die.
- there ar other plastic bits in the coolant system that need to be replaced too: water pump, thermostat, upper coolant pipe. you need to replace all of them. there are aluminum kits not for this.
- The timing chain issues arent that material for these years. That was more a 2010-2013 model year issue.And as long as you change the oil every 5k they will be fine.
- valve cover leaks (im just about to do mine at 115k miles)
- air compressor faults. but you can usually rebuild those compressors for like $20 vs buying new ones
- front suspension control arms every 60-70k miles
- sunroof drains need to be cleaned and maintained or you will get water in your passenger carpet.