Then you have the opportunity to put a tenant in the door to replace you and at that point you'd be profiting and on to your second property.Anyway...

One of the units had mold growing on the wooden window sill in the bathroom.

Once their lease is up we will try again, however I think a more updated home will sell better. there are a bunch of properties in the area that have been flipped and sold for 205k+ that have updated kitchens and bathrooms.

I've door knocked the neighbors and sometimes get more info that I planned on.

He will still receive his commission.Might work on his/her ego a bit but could also open a door for a relationship.

For example, I will email them and wish them a Merry Christmas and offer to do something nice for the property like paint an accent wall, install a new microwave, tune up the furnace, paint the front door, etc.

What you can't prevent is a sober living house from opening up next door and driving your tenants away.

Walking in the front door is a great way to see if you want to go into business with them or not.   20 Questions To Ask Before You Hire A Property Manager  

It occurred to me that a couple of years ago I created a bathroom in a lake house we had and I had to put in a rear discharge toilet (sounds redundant) to avoid cutting into the slab by drilling a hole through a cinder block wall. 

There are other good uses of old structures for firefighter training that may not help you solve your problem but are difficult to simulate due to their destructive nature such as forcible entry (ie breaking down doors) and vertical ventilation (cutting holes in roofs) that you might mention when trying to sell your idea.