Came across a wild deal. Am I nuts?

[Tom De Moya]

Perhaps it isnt wild and I'm still too new. This would be my 4th deal after 3 duplexes. Came across local landlord who has 4 properties for a total of 18 units. 3 6-unit buildings and a duplex. Wants to sell them all as a package. Properties are in a solidly C-Class neighborhood and in C class condition. Not falling apart terrible but not a meticulous landlord or up to my standards. 

Bundling them into 1 deal, this is my math. 

$193k in yearly income. 

$54k for taxes, insurance, utilities. 

$15k for maintenance, (8%) of total income. 

$10k for 5% vacancy. 

$114k NOI.

Asking Price = $700k. 

16.2% Cap rate after expenses with self management. 

3.63 GRM.

Landlord is willing to hold paper. I am running through 2 BRRRs so most of my money is tied up which is why selling financing is key here. My questions: 

How would you approach this? The cap rates are very high compared to so many deals I see here. 

Because the deal is spread across 4 properties, do you see too much risk? 

How would you approach the seller's terms? I am thinking to attempt to get the longest term under reasonable rates to maximize cash flow.