Structures are like people in that the inner condition is reflected in the outer condition, thus any readily apparent deferred maintenance is a harbinger for more problems waiting beneath the surface.

I suggest you not go 30  years with a note going to an estate, your high school buddy may very well look you up with an unpleasant attitude messing up his parent's estate in their elder years, but check with an attorney familiar with estate requirements.......you can also address such issues with a conditional demand feature, if this happens then they can demand full payment in 6 months for example.

Insurance seems a little high.... perhaps because of the area or the condition of the house? 

I can't think of a time with this set of economic conditions.

I would SHORTEN the lease under these conditions, at lease to 6mo, maybe back to 3mo. 

Property owner is financing a relative/friendOtherwise, a seller can sell to a buyer able to get conventional financing and cash outIn certain instances, an owner may be willing to owner finance even if the above conditions are not true.  

If you don't know how to assess condition/age, home inspectors could help with this.

Offer 1 year leases to All 4 tenants under the condition that they pay in full on the 1st and if they don't then I might just have 4 evictions to do in April?

I also know where the distressed properties (condition wise) are located.  

So just by looking at when he bought them, the price he bought it for and what it's listed for now and the condition every property is in tells me a lot about how he operated.