It's never too early to start investing in poker tracking software.
In all seriousness, it's hard to say in terms of
bankroll--I would instead say; do so when you want to start taking poker more seriously. Both programs have a free trial period (60 days for PT3 and 15 days for HEM), and in that time, they can help you earn enough to cover the cost of either one of them (maybe several times over).