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.
If your income is not enough to meet your main needs or when your income allocation does not include reserve funds then investing is not very appropriate, as you mentioned there is a big chance that you will sell the investment at a loss because of urgent needs, before increasing investment capital then fulfill it first, first the main needs and have the right reserve funds and start investing, if the current income is not sufficient for this then look for additional work and then invest with the right knowledge.