But property prices are increasing so the rents but ratio .5 or so  percent remain same. 

Same for a simple, clean, modern light fixture above. 

The problem now is trying to make those big rent increases.

@Quang Tran the simple thing to do is work with a local investor and become a bird dog.

My recollection is that if it is your primary home for 2 out of the last 5 years there is no capital gains tax on the increase in value up to a $250K profit for a single person or $500K for a married couple. 

inherited" tenants like yours are probably waiting to hear from you, so send out contact emergency info and have them respond and include with next rent payment a updated contact sheet,, I'd make an appointment to tour inside of each unit with condition sheet,, the condition from your date of ownership is now what you use for condition move out.. so once that's completed you now know which unit would be tops on your list to rehab and offer an early out to.. if that's a consideration.. you can of course let all tenants know the rent will increase to $$$ when their lease is up and you are accepting 30 or 60 day vacate notices early, they'll be prepared. 

It has been many years but tax is not increasing much. 

On the case of the tenant you don't have to evict them you could do simple what I did years ago when I use to buy HOA foreclosures that have tenants, just ask them to leave and charge no rent for that time, yes it's that simple tell them they were scammed if you haven't already but be the good guy I usually say something like this "look this happens sometime you are in a bad position here your lease is not valid, I usually give people a week to leave but ....

No DOS issues if you follow this simple step. 

Make friends increase your circle of influence - Hire a private detective - they are good at finding people (give his a piece of the profits)Check the death notices or search government record for certificates of death, check the obituary for next of kin - contact them.