Default Fixing a phone that won't start (buying off cheaply online)

I'm looking at getting this phone off a local auction site. It's in perfect condition but the owner says that "suddenly one day phone was on charge and turned off won't turn on". Is it possible for me to get it and try to fix it?

If I can get into recovery mode, how should I push a custom rooted rom onto it? Or perhaps should I download an official firmware for the S4, and push it to install via the official way of using Odin + download mode? Can't seem to remember parts of it since the last time I dealt with Odin was 1 1/5 years ago on my S3.

PS. Is download mode the same like on the s3? Ie, power button + home + volume down

EDIT. Called the seller, apparently the phone doesn't even display the samsung logo. Should I give up? Could be some hardware issue or idk.