All people, nominalist as well as realists, can believe in: One day, I will die. Or more general, they can believe in:
One day in his future, each living being will die.
That's the most simple hypothesis about our future. No case is known which contradicts the hypothesis. Instead billions of cases from experience support the hypothesis. In addition, there are many theoretical arguments which make the statement a plausible hypothesis.
"To die" means that a certain process ends. The noun "death" does not refer to a new entity. It is just the nominalisation of "to end living". Nominalisations of this type can be helpful ways of speaking. But one has to keep in mind that they do not refer to new entities.
The alternative, whether negative entities like death refer to an existing object or are just negations of positive statements, is the subject of lengthy discussion between nominalists and realists. IMO these types of discussions seem a bit far fetched. In any case, they do not decide whether the original hypothesis is true or false.