every account has a 2 week free trial, if he's already used his you could set up bogus accounts for each time he wants to play online and take up the 2 weeks free until it expires then rinse and repeat - once the bogus account is setup you make his PS4 the primary one for that account and he can log on as himself and play online. Just be aware that whilst this is a good stop-gap for online play when short of cash, the PS+ games are account locked.
1) log in with new account
2) set up bogus account (you will also need a bogus email address) -
be sure not to add any CC details!
3) set the PS4 to primary on that account
4) go onto the store and activate the 2 weeks free PS+ trial
5) switch back to his account and enjoy 2 weeks of free online!
WRT 2) I buy game digitally to share with my daughter who is at uni - as an example what I do is set up a new yahoo account e.g.
newgame2016@yahoo.co.uk then I set up a new PSN account using that email and mirror the account name for consistancy (i.e. the PSN account is called newgame2016). Passwords won't matter for you because you'll only do this action once - so they can all be the same (e.g. FreeAccount2016 or something else - just remember to make sure you do not add CC details!!)