Several mitigation techniques can often significantly impact your costs.

SOME state real estate licensing agencies believe that most wholesaling techniques violate state laws when performed by non licensed individuals.  

If they are crossed it could cause *some* electrical problems.Laptop power supplies in particular are very tolerant of a wide range of voltages, often rated for 100-240v or more.

Also if you search the platform for "cap rate" you will find a treasure trove of info.https://www.biggerpockets.com/renewsblog/2011/11/16/capitalization-rate-%e2%80%93-techniques-to-speed-up-your-decision-making-part-iii/

Finally, if the actual numbers are very different that what was represented in the listing, like others have said, this is a very powerful tool for renegotiating once the property is off the market (under contract).Good luck!

He should be hitting economy of scale by now, so his buying power is about to explode if he is doing things right.A handful of years ago, a guy in my area pulled some investor capital and bought a bunch of houses while paying them 8-10% interest only, BRRR till he paid them off and upgraded bank financing.

This same house has a 150 foot run of 10 gage wire to power the stove top.

I have the house, driveway, walkways, fences, decks and roof power washed to bring the materials to a common color - while my competition has gray fences - I bring mine back to a beautiful wood finish, my drives are one consistent color, etc.  

It would be pretty interesting if power play comes in and you still have the tenant legal system on your side.

Unless your lease gives you the power to ban guests based on behavior, I would say that you are more or less out of luck unless you can get a restraining order against him based on his behavior towards you.