The neighbor appears to have evidence of some barking and party noise on video to attempt to substantiate his claims.Normally, aggrieved residents could call Animal Control or the Police to deal with noise issues.

True to her character and evidence of my lack of skills in dealing with PITA tenants ... 

Yours is a old business practice with no evidence to support the logic.

I found out that one of the tenants (family with one kid and another on the way) earns more than I do at my job (they probably make between around $45k between the two of them), and in the other unit, it's a couple with 3 kids and a dog, where the mom works full time (in a department store) and the dad goes to community college and gets stoned at home during the day (but I have no evidence of that other than personal observation when I repair stuff over there).The point is, as each week passes and I lose money paying for the loan on this property, I feel PWND.  

You can look at our national budget, or that of places like Greece and Portugal, for evidence enough that anything mixing democracy and budgets has the potential to produce idiotic results. 

If you have evidence the mom is living there (it seems you do), you have every right to add her to the lease and ask them to discontinue using the guest parking spots.  

Obviously there are individual exceptions and they will be evident within a few months.

So, evidently it must be doable and in the greater sense, profitable.

The landlord then documents their finding of the abandoned apartment, including evidence of the tenant's abandonment, such as no rent for the last month and no possessions left behind.

And surprise, he found no evidence of bedbugs(and Feh did not wish to show her son's "bites" to the exterminator.)