Withold rent, get served an eviction notice. 

In fact I have a clause in my leases that if I find out anyone is doing so it will immediately terminate their right to remain in the lease and they will be served notice. 

We had tenants renting for 4yrs, when we got to the property after they moved out we noticed a large oil-stain in the driveway as well as various other smaller oil stains in the driveway.

For example, one steady red flag I've noticed is if the tenant tries to overly sell themselves almost with a rehearsed pitch before you even start asking questions especially. 

Hellen  Keller may have not noticed however I certainly could with just a cursory review of the property. they don’t actually know the extent of the roof however note possible deficiencies.  

We went directly to the listing agent, and we noticed that it was on the market for a very long time.

Start NOW with a pay or quit notice , file for eviction as soon as you can .  

With interest rates where they're at right now, we're starting to notice the margins on deals not making sense, unless you're getting into the right asset. 

If the tenant violates the term of the lease, you'd file a 30 day notice to quit.

It should also contain the procedure for requesting maintenance, paying rent, rent due dates and late fees, and if you plan to raise the rent soon, may as well give notice of that too.