Need a MBP for basic tasks while on the road, at a budget price ($300AU)
I never feel that money spent on old computers is well spent... but actually, at that sort of price (people may be missing 'AU' in that dollar price, which makes a difference) it might actually be worth considering. Do take into account what
@EugW said about fitting a SSD and min. 4G RAM - so don't go much higher.
If you were prepared to spend more money, I'd go for a newer MacBook Air, but if If AU$300 is your price limit then I don't think you're going to do better without going to a PC or tablet solution.
I have a 2010 13" MBP (4GB, with SSD, still running 10.9) that I use as an emergency backup, or when I need a basic computer on-the road and don't want to lug my 17". Its perfectly usable for general tasks. You can't get away from the fact that its an 8-year-old computer, but you're not trying to do anything that people weren't doing 8 years ago... Be forewarned that it
might be excluded from the next version of Mac OS (but the current version will be supported for several more years anyway) and - obviously - if it goes wrong its going to be "beyond economical repair" - so don't count on it lasting you too many years.
If I recall correctly, the NVIDIA motherboard-chipset-with-graphics in the Mid-2010 13" MBP is a keeper (and the reason why that model stuck with Core 2 Duo rather than i-series processors with inferior integrated graphics) - it's the 2010/2011 MBPs with discreet graphics that are best avoided.