You shouldn't keep secrets from potential significant others.
Zack is dating Kelly, but he has a significant amount of debt.
Zack wants to propose to Kelly.
Zack proposes to Kelly and mentions his debt.
Zack proposes to Kelly but does not mention his debt.
Kelly will be able to judge for herself if she wants to take on Zack's debt.
Kelly will be negatively affected by Zack's debt without her knowing it.