If you try to avoid this inquiry by depositing the money systematically in smaller amounts, that is called "structuring" and they have algorithms to detect this behavior and then they will really want to know the deal. again, if you're doing everything legally, then go to a bank and deposit your money and answer their questions honestly.

The excuse could be , "I lost my job " "My dog died ", I have to take care of my sick mother "  My job transfered me "  ( Only military  is acceptable )  .  

This method is mathematically inferior but tends to work on individuals who are greater affected by short-term behavioral changes (paying off debt feels good), and this is a majority of the people in this country (which is why Ramsey is so popular). 

You're getting frustrated and it doesn't seem like he or his new girl really have any clue that their behavior is becoming an issue for you. 

I know bird dog deals that are executed on usually go for $1000, what should I be paying him for finders fee?

Yep - I started buying houses for under $5,000 - therein was my wake-up call - my street seminar - the school of "hard-knocks -- guess what - I survived and made some serious profits from junk real estate in Baltimore.Looking back on all those cheap houses, I guess I was fortunate to have very little knowledge and even less money - I had no choice but to learn the creative aspects of investing - I used credit cards, I did subject-to's, delayed settlements, financing companies, tax sales and foreclosures -- I was forced to learn how to fix these dirty dogs - I would get on roofs with Jack-Legs to learn how to do them myself, hanging dry wall, the art of mud, electrical and carpentry ----- WOW was I ever lucky to be unemployed with no money and a force that pushed me to achieve cash flow or equity.

If prior leases must in fact be honored the PO did have the following clause, "Illegal, unsafe and repeated rude or inconsiderate behavior to residents/tenants by other tenants or their guests can be considered grounds for eviction."  

It's always easier to catch a dog when you run away from it then towards!

Additionally, performing a background check can help you to get an idea for any type of domestic spats or criminal cases which could be indicative of patterned behaviors you wouldn't want of a tenant.

What's the best way to deal with this as I prefer to keep the good relationship we have and minimize any bad behavior and resentment from the tenant?