I've talked to a lawyer and he recommended us to install a security camera in the laundry room with intention of buy out or eviction plan.

Camera's always aim for "grey", so a white wall with a bright window will look dark.

He's going to have to bring out his camera and his 100-ft snake and attempt to unclog it.

I also have high-end cameras.

Six months isn't much time at all, and that's especially true if you plan to waste the first 10-20% of it on unimportant stuff (at least unimportant at the time you're doing it).Reminds me of the Simpsons episode where Homer gets into a contest with a professional eater to see who can eat a 6 lb steak the fastest...the contest starts and the camera pans over to Homer who is buttering a piece of bread. 

They get places where you do not want to get (attics, crawling spaces), they use infrared cameras to see inside walls, they will tell you if outlets have grounding, if AC is cooling, if Water Heater is missing a expansion tank.

Thanks for sharing the video I subscribed to him, it looks pretty interesting, he needs a camera man and editor, but Im not complaining. 

Is it possible to just drill a small-ish hole and send in a camera?

Obvious cameras deters most and will be the cheapest route.You can probably get by with locks on the doors, cameras and a camera at the gate that can activate when the gate is opened.If you have serious concerns, I suggest you speak to a security specialist, your attorney can tell you the degree of security needed to keep you from being negligent and keeping tenants reasonably protected. :)  

I gots ten charges of tresspassering cause they done got me on the cameras creeping around.