Long Term tenant - Constant pain

[Dean Klein]

I purchased an upper lower duplex Nov of 17 and inherited both tenants, recently the upstairs guy left and I rented the apartment for over $100 more than he was paying. The downstairs has a tenant who has been there since 2013, it's a married couple with no kids, they take care of the place but the guy is a pain, he is in his 50s and constantly complains about stuff and thinks he owns the place basically. My new upstairs tenant moved in yesterday and he is already complaining about my new tenants stuff sitting next to the garage (stuff going to the dump) because he then "can't mow there". He's got a problem keeping out of other people's business. This guy is paying $625, and market rent for his unit is around $750-800, my first thought was to just raise rent but I know that will likely cause an issue, he already complains and I don't want to deal with that. Should I just give him notice and turn the unit? He works for the city that the property is located in and constantly keeps watch on the place throughout the day which is definitely annoying considering if I'm there doing something outside, he has to stop and ask what I'm doing...