I disagree with you mate, you don't need or have to get an additional source of income before you can be aggressive in your investment, aggressiveness is a function of how big your discretionary is or aggressiveness is as a result of strong discretionary income. Remember when you are Investing aggressively you don't need to touch any other funds than your discretionary and anything that makes you touch other funds is a wrong thing or wrong approach because it's only our discretionary that is meant to be touched while we carry out Bitcoin investment whether aggressive or not. All an investor need to do before investing aggressively is to build up a good and huge discretionary and everything is settled.
With same investment capital, you can invest gradually or aggressively, it's my thinking, that means I disagree with you.
Investment aggressively or not, it does not require to have extra (additional) source of income or investment capital. It's only matter that whether you want to DCA gradually or want to purchase bitcoins aggressively. Assuming with same investment capital as $1,000, you can gradually DCA in 10 months or your can purchase bitcoins more aggressively in 5 months or 3 months or 2 months.
Of course with DCA strategy, it's always better if you can have regular investment purchases and can have new investment capital with time rather than 100% rely on your investment capital at beginning and plan how to use it with time. Like you can start with $1,000 investment capital, plan to use it for purchasing bitcoins in 10 months, but it's better if with time, each month you can save part of your income and have like $50 or $100 more new investment capital. That will sum up your investment capital to bigger than $1,000 with months.