builder has taken loan from the bank for his project

Pardon my naive question but then I am not so savvy
In real estate deals.

I do understand that builders take loans from banks
To finance their projects. My naive query is that is it OK to
Book an apartment in such projects? What if the builder
Is unable to pay back to the bank? What would happen to
The flat that the customer has booked in that project?

Thanks
P.s I know this is a generic question. Please move it to
Respective section if mods think so.