Ultimately I want to replace mine and my husband's income with passive income from investments.That being said, I have worked with at risk children in schools doing behavior intervention for the last 13 years.  

We keep domestic animals (dogs, cats, horses) and some animals for food (chickens, pigs, goats) and that's it. 

Then start with the one that require the least amount of money (bird dogging).

Not sure if it's a hive in a tree or an actual bee box but the bees are stinging my tenants and tenants dog! 

Avoid swimming pools, trampolines and dangerous dog breeds.

I can't say if this would be an option but my friend gated her stairs at the bottom and it helped this was more of a way of managing  her own kids and the dog.

They have been paying on time since I bought the property and have been good tenants; however, they both have cats and dogs, are smokers (outside), and the amount they are paying is ~$200 below market for unit A and ~$100 below market for unit B.

Those veterans that, unfortunately, fall into the trap of thinking it's normal for 30%+ of one's income to go towards car payments while on active duty (where this is perfectly normal), generally cannot qualify for mortgages until they realize that this is only normal in the military where you don't have to pay for housing, food, etc.I could do an entire rant on how/why the military is doing a disservice to the troops by allowing this irresponsible car behavior to be normalized among 18-21 year olds (& in far too many cases their junior to mid-level NCO leadership), but that wouldn't be helpful to OP.

So, if ARV is 200k and it needs 20k in work to flip and the bird dog wholesaler wants 5 k spread.

We did live in a SFH converted to a duplex as renters before we bought, and aside from the upstairs tenants having a dog against the lease we got along well with everyone else who lived there.