All the belongings would normally be handled by the Abandoned  Property regs for your State, but as family is already aware, I would ask them to remove all the contents within 30 days.When one party to a contract dies, so does the contract so the lease is no longer in effect and as soon as the contents are gone you can cleanup and seek another tenant.Prepaid rents you hold are 'unearned' and the deposit should be handled as any other move-out.In Calif, a landlord must notify the next occupant that there was a death in the unit -- verify your State requirements. 

I could technically quit my job and live off the profits from these 4 homes today but I am more risk averse than that and would like to have more cash reserves after they've been depleted a bit to acquire these homes.I'm always amazed how people are able to build a portfolio of 40, 50, 100 homes and haven't quite figured out how to do that unless most of those homes are under $100,000 (or much less) and they've been doing it 10+ years, but you do hear of it on the Bigger Pockets podcast.So, given all that:1) What am I doing right?

If  they do move, you clean up the apartment, raise to market and rake in the dough!

I would have charged someone else $500 to clean up the mess , so I saved $ 500 which paid for my trip .

It will cost quite a bit to clean up (haul out old trailers (3K to 6K per trailer) + some additional legal consultation costs I imagine) then redo systems.

Will keep and clean up appliances.

If a LL doesn’t believe in charity or social commitment beyond keeping a safe building in exchange for the rent check, looking at this purely financial, some of the hardline answers may have never experienced a regional or national downturn and may not have stopped to crunch the numbers:-1 to 2 months rent deferred over the six to twelve months OR -3 months plus eviction costs and another month of vacancy after clean up lost with no chance of recoverySometimes good business is also good for people - so when we have the opportunity to do good, why not take it?

I use Ben Moore’s advance product for topcoat, oil based water cleanup.  

It may not be too late to clean up the paperwork and get in front of it but I'd recommend that you speak to a lawyer in regards to that process.

It was sold half way through the flip and I didn't have to worry about finding a buyer.I always have my team clean up and repair any hazards before letting a tenant buyer move in.