The sharing of durable goods in a dynamic ownership economy is attractive, since it has the potential to realize gains from trade via short-term transfers of usage rights. We develop a model in which a set of agents, who are heterogeneous in their likely need of a durable good, make purchase decisions and then have the option to participate in a sharing market contingent on a realized need. The agents' purchase decisions are compared to a situation where ex-post sharing is impossible. The impact of sharing on product sales is ambiguous: for low-price products sales may drop, while for high-price products the number of consumers who decide to become owners may actually increase. Our analysis extends to a sharing market in which prices are negotiated bilaterally in a Nash-bargaining framework. The resulting negotiated-sharing equilibrium allows for a realistic supply-demand imbalance in the sharing market.