Sometimes they can make the property negative cash flow or in a worse case scenario prevent you from even leasing the place to anyone but family members.

If you are looking at a small multi-family of four units or less:Rent RollReview all leases, addendums, or other agreementsTenant payment historyAny violation notices, delinquenciesList of all maintenance in the past yearSchedule of capital improvements in the past 3-5 yearsUtility bill reviewP&L for current year plus the last 1-2Service contracts (landscaping, cleaning, snow removal, etc.)Inventory of all property owned by SellerThere may be more but this is a good start.

Do a search for Subject To, Wraps, Lease Options, Owner Financing, Land Contract.

Look into master lease agreements.

How many evictions have they handled at the property (may speak to tenant selection quality), how many tenants have left mid-lease (also may speak to the quality of the management, bad managers lose good tenants)? 

That's when the upper unit tenant called me, as he's never really had this problem before and really didn't think he needed to call me because they are all adults but felt it was a big enough issue and now he is thinking about not resigning the lease for next year.  

A residential home, already divided into duplex and has 2 current tenants  (one's lease is until 3/31/18 and the other is 5/1/18). 

@Byron BohlsenI make all my tenants get renters insurance per the lease paragraph and  I tell them: " file the claim and have the adjuster check the door for damage as well. " Renters insurance is about $150 per year. 

Rent is $1950 (we just increased it a couple of months ago when the lease was renewed), and we've had only a single tenant.  

Now I need a lease for them to sign.