Just as a sensible income is needed to start investing, 2 more things are needed
1 Basic knowledge about Bitcoin
2 Faith in Bitcoin
I wonder what type of sensible income you are talking about because to the best of my knowledge, their are so many guys out there that wish to invest in Bitcoin that are earning a sensible income as you called it but still can't figure out their discretionary income, what an investor need in other to invest in Bitcoin consistently is a discretionary income and the will to hold for a very long period of time, because if he has the will to hold for the future, he will put down measures that will make him develop a strong holding hands, like having an emergency and reserve funds in place to protect his investment against any unforseen circumstances that may arise in the future.
You're absolutely right Futurexxx in your assertion. It doesn't matter the size of a person's income, if he's not able to figure out his discretionary income, it'll be impossible for them Invest in Bitcoin, even if they move ahead to invest in Bitcoin without actually figuring out their discretionary income first, they'll end up making a huge financial mistake along the line which could potentially send them back to square one. This is the mistake that most people often make, they feel an individual's chances of investing in Bitcoin is dependent on the size of their income, which is in fact a wrong perspective of approaching Bitcoin Investing. Once again, people don't accumulate Bitcoin with their income, but discretionary income.