The problem is his business will devalue your property. 

Even though downtown is a very hot market right now adding additional inventory will give consumers more options and in turn devalue your property!

Even though you area may not support full duplex style house hacking you CAN find a devalued, single family, fixer upper and house hack that way!

A rent 10% below market has devalued your property by 10%.

Would it help my case by letting him in (no copper, dirty etc) or will it hurt my case (in decent shape) UPDATE - just spoke with attorney, he says let them in, the missing copper / stained carpets should devalue the house further...

Not the only driver but a major one.Good assessment.I like to think of rising real estate prices as a reflection of the devaluation of the dollar.

So I am not charging the tenant more but keeping pace with the devaluing of money.

@Joe Villeneuve  my comments are more directed towards the camp who's motto is" I just want cash flow and appreciation is icing on the Cake"  but its all a personal preference and risk tolerance and historic movement in RE values.And when your born and Raised in the Silicon Valley like myself and started in RE in 1975 I have seen the huge run ups.. so of course I just can't have anything but an appreciation bias for sure..   1975 home in Cupertino were I was raised my parents paid 25k for it.. today its worth close to 2 million and its just a Valley track house nothing special 3/ and 2 with a bonus room and 2 car garage on a 6k sq ft lot...and what you don't have in the bay area is with the very very tiny exception you have NO area that devalued at all...

Rental units devalue a building and are often resented by other owners. 

But still, rental income investments in single-family homes are still widely popular around wealthy people here, mostly relying on a "safety investment", meaning putting their money where it will not devaluate with inflation and maybe get some appreciation over time.I was able to get 4% Caprates with 50% down payments.