Hey, new user.
I've received PSN accounts as vouch copies on MPGH and I've never got banned. Before you get an account you have to ask the seller whether or not the PSN account is cracked, carded, or a personal account. If it is a cracked or personal account, there is virtually no chance of you actually getting banned. You just have to make sure that you log into the cracked account as a different user on your PS4, activate your PS4 as the account's primary PS4, then download the games.
If the games on the account are carded (meaning the seller put the games on the account using stolen credit card information), then there is a chance the account itself will be suspended later on when the charges are disputed by the actual owner of the credit card. It is possible that Sony can then ban your PS4 from using PSN.
I recommend you purchase either a cracked account or a user's personal account, because that has nearly no ban possibility whatsoever.