They can build a better future by investing in Bitcoin  .  Anyway they should follow the title, find a side hustle to earn extra money,  Separete a certain percentage of the income to DCA in Bitcoin, a 5% of the income does not hurt.  One can tighten their belt to have a better tomorrow. 

We have witnessed how Bitcoin enables huge profit in the long run.  Assuming a person who just have enough money to sustain his family in his job, finding a legal side hustle to earn extra money and put part of it in investing Bitcoin, do it for two to 3 cycle, and I believe that person will have enough money to live a more comfortable life in the future.

If one is lacking even with a stable job, one should either look for a better-paying job, do a side hustle, work smarter or learn a better financial management program while tightening their belt.  Then when everything is ok and the peson can have some extra from his paycheck, then he can start accumulating BTC.