@TJ Addison I would wait until you have the unit back in your possession to clean.

Please read my post about Alabama tax sale redemption rights time periods:  https://www.biggerpockets.com/forums/70/topics/181...As soon as an investor receives the tax sale certificate, he/she is entitled to possession. 

For me it's 5 months and 10 days unpaid rent only because that's how long it took in court to get an order of possession and then have it enforced.  

In my area, if they don't leave the keys, it can be argued that they haven't legally vacated, and if I change the locks they could claim they were still in possession of the unit.

If they never pay and build a balance the comes close to equaling the amount of their deposit, we already have possession and can evict at our discretion since we have already taken them to court. 

Apparently my great aunt passed away a few weeks ago and left her only possession - this house - to us.

Since you already have a signed lease and it would be more convenient for you to get the keys to him early, anyway, if it were me, I'd write up an addendum changing the lease start date to Sept 29 as long as you get first full month's rent + 2 days' prorated in certified funds before possession.  

A brand new oven spontaneously set fire for no reason during self cleaning mode, the fire did not leave the oven, but the home is unsafe for four days and her possessions have smoke damage?

Ideally, I would like to get possession of my unit un occupied asap.

We meet with them in their unit and do a walk through to document the condition of the unit at the time we took possession.