I think someone can start with the little they have if after Investing it won't choke them later but if someone knows that if after Investing in Bitcoin their responsibilities and there needs will choke them then I will suggest they don't invest in Bitcoin at all because it makes no sense after investing you went back to sell your coin because of your inability to take care of your needs and wants.
If the person feel the big contract will definitely come and they don't have all it takes to invest and maintain their investment at the moment I will advise they wait for the big contract and while they are waiting for the contract they are also hustling to make things work out so should in case the big contract doesn't work out they won't be hopeless and stranded. Remember it is not every time, it is better to start small because sometimes you will regret why you started small.
I think that you are making it looks complicating here, you don't necessarily need to have it all to start investing in Bitcoin, all you just need is a discretionary income to start your Bitcoin investment, and take note that you may decide to invest this week, but if you didn't have a discretionary income next week end, their is nothing wrong about that, you might skip that week and buy again anytime your discretionary income is available, so why am saying this is that you are not obligated to buy every week or month ending, you only buys when your discretionary income is available in other not to get involved in unnecessary pressure that may affect your Bitcoin investment.