I prefer folks leave stuff alone. I don’t want cheap aftermarket parts in critical areas. Plus it’s a waist to have folks replace all the front brakes with OEM spec stuff, cause I’ll just toss it going to Tundra stuff.

But I do all the work myself, so only parts price is a concern and most of the stuff can be wrapped up for $1k in parts.

I look for no rust. Hate dealing with that. Once rusty there is no full recovery.
And good maintenance, preferably good oil changed more often than every 5k. And no goofy modifications. And no body damage. Body work is expensive and annoying to deal with.
Plus the rig needs to be such that it can be turned into what you want to end with.

Like don’t buy an auto if you want a manual. Don’t by a limited if you don’t want all the plastic gingerbread, and wood interior.

Locker can be added for about $600.
Tundra brakes about $500.
Timing belt and valve cover gaskets $400.
All suspension bushings replaced about $300 wrapped up with a lift.
Center console swap $100.

If it’s going to be your daily, then buy something that’s in good running shape and only needs work like listed above that can be tackled on weekends when funds allow.
Make a list in order of importance and spend a car payment each month buying the parts and working through the list.

Ask questions on here. Some of these guys are 4runner whisperers with amazing skills, knowledge, and generosity.