When infinite-lived agents trade long-lived assets secured by durable
goods, equilibrium exists without any additional debt constraints or
uniform impatience conditions on agents' characteristics. Also,
regardless of whether assets' net supply is positive or zero, price
bubbles are absent when physical endowments are uniformly bounded
away from zero. Otherwise, bubbles may occur, even for assets in
persistently positive net supply and for deflators yielding finite present
values of aggregate wealth.