Kevin,
Congrats sounds like a great find. Here's what has worked for me:
1. Intro letter to tenants requesting updated contact information, maintenance problems, how to pay rent / contact our office etc.
2. Fix the outstanding maintenance issues.
3. Send each tenant a letter letting them know you need them to sign a new lease that will contain a rent increase schedule. Give a deadline for notification of their intent to sign a new lease or their plan to move.
Consider a $200 a month increase every 3 months may not be doable for most tenants. Depends on the class of property.
Talk w/ each tenant, work with them if necessary on an increase schedule that won't cause them a financial hardship but helps you achieve the increase. Be prepared to work with them on a plan to move.
You can make the argument the cost of moving is more than the cost of the increase. Most tenants in my experience don't calculate the cost of a move.
Calculate what it would cost you to evict them if they won't or don't move willingly, that's a very real possibility.
4. What if they all decide to leave, can you carry the mortgage, etc. while renovations happen? A way to protect against this is to stagger the new leases / rent increases.
5. Consider holding 1-2 units slightly below market ie. $50-$100 a month. While I want to maximize profit, I also want to keep my properties stable. Think about your renovation and turnover cost.
If it takes you $8-10k to renovate a unit, not including cost and time to find a new qualified tenant etc. a $50 -$100 a month difference in rent for a known / stable tenant in my opinion outweighs the the full turn prospect.
Hope this helps.