Starting Bitcoin investment with little capital will be very challenging mostly if that happens to be the major survival option of the investor. And in cases where the investor plans on using the proceed to solve their needs they might end up selling when the price have dropped just to settle the pressing need of that time.
As experienced investors are there measures that can be imbibed by new investors with little capital to help boast their capital. Some will want to mention patience which I will agree to but in situations where the money is needed to meet an emergency need how to you tackle such situations. Your formula might be a saving approach.
We can not know about future and I agree with you that our plan will save us.
A safe plan is never use 100% money for investment even it is an investment in Bitcoin.
My plan is using 70% of my money for investment, 20% for life expense and 10% for emergency.