Perhaps you could check with his phone company to see if
their lines in that area support ADSL, if so then he could get
an inline-filter so regular voice items (phone) would still work
and he could have fairly quick internet over the DSL, too.
The DSL would use a special modem, so the 'phone line'
could carry the other signal at higher rate; and a filter is
used to reduce the signal for a conventional phone, then.
Only one line; but it would cost more than using dialup over
older phone line. The company I'd used dialup over for awhile
chose to replace all their copper heavy cables with twisted-pair
DSL lines, through the woods and 30+ miles away from town.
This was problematic as it hadn't been done there before. Later
on, after customers were paying for defective service & also doing
troubleshooting, the company got it right. Once lines are replaced
the need to use a special filter to limit bandwidth for regular phones
is necessary; even if the internet is no longer used.
Some companies rolled this out, in advance; others sat on their
hands and didn't upgrade regular phone lines to this standard.
If he has DSL twisted-pair lines into his house or residence, the
company can offer faster internet, via a DSL modem, for extra.
The problems with dial-up are many in this information age; because
the packets of data and other bits are so much larger and take time
to download or upload at the imagined 56K (& that's often much less.)
Depending on the location or region, other options (for their fee rate)
may exist to have a fair access to internet for simple computer use.
A trial-run may be to get an older Mac with older software & modem
to see what kind of actual 'un-performance' the dial-up may bring...
Macs with built-in 56K modems + original OS X are limited online.
Good luck & happy trails! 🙂