New 6 Unit - Tenants Paying Way Less than Market

[Bill Jones]

Hi everyone, I am a new landlord who just purchased their first six unit. It's a great building and I was able to get it off market from an owner who has owned for 40 years. 

The only issue is four of the units are paying far less than market rate for rents. Some are paying 700-800 for 1 bedrooms with heat and utilities and comparable local rents are in the $1300-$1400 range and there is ZERO rentals available in this area due to pharma industry uptic. 

Two of them are holdover tenants with leases that expired a couple months ago however they have been there 5+ years so I believe they are entitled to 90 days notice. 

When I close should I send notifications of rent increases? I was planning on raising to $1,100 a month for the 1 bedrooms. (This can be $300+ more than they are currently paying) They will find nothing in this area near this for rents. I feel for the tenants but they have had it good for a long time and I have to treat this as a business. I'm willing to take the gamble on them leaving as I will be able to rent them for $400+ more per month with new tenants. 

Is there a good template letter somewhere for raises? 

I am excited and a little nervous to embark on this new journey.