This extra road frontage now also qualifies my property to be able to be legally converted into a triplex from a duplex.

I agree with the others when they say to hire a PM; a property manager will have access to better screening and fraud detection - and hopefully can add some protections in the legal arena too.

I recommend legal advice from an attorney.

Do not rely on it for legal advice.

I've printed out a Notice to Quit and will post it on their door for legal protection.

Hey Santosh,As of right now you're extremely exposed regarding insurance and I'm going to assume legally as well.If the home isn't registered as a legal multi-family with the town that's something you'll have to correct ASAP and make sure the home is up to code.Insurance wise as soon as they find out what you're doing they'll cancel you as the risk has changed from a single family owner occupied home to a multi family owner occupied home.

@Kash Tacke legally, you would need architect drawings to get approval from Detroit Zoning Board.

This is assuming the way you notified the tenants of the new rent was considered legal notice in your market. 

Hiring a PM can save you time and headaches by handling tenants, maintenance, and legal stuff.

(e.g. peace w/ Israel, gambling legalization, etc.)