Tenant Has Become Ill and Hopsitalized, Others have Occupied the Property

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I have a unique situation. I closed on an occupied rental property on 30 August 2013. Rent is due on the 1st and is $600. The tenant on the lease has become ill and is currently hospitalized. As a result the tenant's son, the son's girlfriend and tenant's daughter have moved in. The tenants lease expires 23 September 2013. The previous property manager did not ask the tenant 30 days in advance if they'd like to renew the lease.

My questions/comments are as follows:

1) How can I be sure to recoupe rent for September 2013? Today I introduced myself in person to the son as the new owner. I got his name and cell number.

2) Should I take new applications and/or create a new lease with those occupying the property as tenants? Meanwhile I'll accept a partial rent payment for September 2013 since the lease ends on 23 September, $460. When the new lease is signed I'll require the remaining portion, $140. No deposit should be accepted, only if the original tenant is not on the new lease.