Can I sell his things to pay rent?
I would advise against selling his junk.
Why?
Read your state's law on what landlords/roommates must do with abandoned property:
The statute in Indiana regarding abandoned tenant property:
Indiana Code Title 32. Property § 32-31-4-2 | FindLaw
Keeping or Mismanaging Abandoned Property - When a tenant leaves items behind after vacating the property, the Landlord must treat it as abandoned property.
Contrary to what you may think, you cannot simply dispose of the items or keep anything that you want. There is a due process that must be adhered to in order to legally deal with any abandoned property.
Title 32 of Indiana Code
2012 Indiana Code :: TITLE 32. PROPERTY :: ARTICLE 31. LANDLORD-TENANT RELATIONS :: CHAPTER 4. MOVING AND STORAGE OF TENANT'S PROPERTY states:
Summation of the law on abandoned property in Indiana:
* A landlord has no liability for loss or damage to a tenant's personal property if the tenant's personal property has been abandoned by the tenant.
* For purposes of this section, a tenant's personal property is considered abandoned if a reasonable person would conclude that the tenant has vacated the premises and has surrendered possession of the personal property.
* An oral or a written rental agreement may not define abandonment differently than is provided in subsection (b) [of the statute].
* If a landlord is awarded possession of a dwelling unit by a court under IC 32-30-2, the landlord may seek an order from the court allowing removal of a tenant's personal property.
* If the tenant fails to remove the tenant's personal property before the date specified in the court's order issued under subsection (d), the landlord may remove the tenant's personal property in accordance with the order and deliver the personal property to a warehouse under section 3 of this chapter or to a storage facility approved by the court.
* If a Tenant doesn't claim their property within 90 days after receiving notice, the warehouse or storage facility may sell the property.
* So in essence, once a Tenant's abandoned property is moved to a storage facility, you should take yourself out of the situation.
NOTICE, the statute fails to discuss the duty owed to a roommate.
Because the duty falls to the landlord.
Selling the property could cause you grief.
If the roommate (deadbeat) squawks, the LL will likely find out what you permitted.
This is why one should never allow a roommate NOT on the lease to LIVE in the unit!!!
You, however, permitted to person to live in your unit ABSENT permission from the landlord.
There are no laws about property abandoned by a roommate left with a roommate.
The landlord/tenant laws are written concerning property left in the unit, which is owned by a landlord.
Common sense suggests you attempt to contact the person and plead with her/him to come collect the junk.
Common sense suggests that selling the junk would likely inspire the deadbeat to sue you for junk worth 20 times what the junk is really worth.