The lad and his tradey mates all use Boost although it's not supposed to be for biz use and they state 'reasonable use limit' in that regard. Tradeys largely use phone and sms for clients and suppliers so Boost don't seem to care with lots of that use as it's data that causes congestion. Mum and I both use Boost as you can't beat Telstra travelling.
That's the point too with fixed broadband if they tell you you're on RIM copper or can only get ADSL it will be flaky and slow whereas your folks can have good mobile connection. As well once you get outside the metro areas a lot of the cheaper broadband suppliers go missing (I can't even get Telstra's Belong offer in metro Adelaide)
Just a tip if they go onto mobile full time get a bigger screen for old eyes and in that regard DS have the Telstra Blue Tick 5" Lumia 640LTE 5" for $239 or the bigger 5.7" 640XL for $339 at present and both listed as first upgrade to Win10. We're both on Windows phones (mum 640 and me 735) and they're great bang for buck phones and easy to learn for oldy non-gamers and marginal apps users. Can't beat Here Drive for an emergency car GPS either and we're used to Windows on PCs.
In case you were wondering the BIL and I and the shooting mates, etc have all been there with this stuff with our parents' generation, although some of us have only picked up smartphones in the last couple of years. Windows and Boost for cheap dummies who still actually talk on phones