Investors in Blackstone Group LP’s debut sale of bonds backed by U.S. rental homes are agreeing to accept more risk than in traditional mortgage deals by at least two measures, along with an unproven business.

Blackstone’s Invitation Homes borrowed more through Tuesday’s deal relative to the value of the houses serving as collateral for the bonds than recent residential-mortgage securities, according to data from ratings companies. The cushion to cover interest payments is also smaller than in deals tied to apartment complexes. Monthly rent checks from 3,207 properties will service the $479 million of debt.

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