Analysis needed please

[Dan Simpson]

In my area is a walkout basement duplex for rent. Each side has approximately 2,200 square feet and 3 or 4 bedrooms. The duplex is in good shape and in a good convenient neighborhood. Market rent for each side is  $1,000 per month.

The owner is selling it on terms for $198,500. He wants 10% down with him carrying the rest at 4.5 interest, amortized for 18 years. After 5 years, the seller can refinance, as he will charge a pre-payment penalty if someone refinances before that. He wants retirement money... Anyway, the total payment per month with taxes and insurance would be around $1,450. 

I was thinking of living in one side of it eventually and renting the other side out, but for now, there are tenants in place. One is moving out in January. 

My thinking is that this might be a really good deal. Similar duplexes in my area selling for around $200k only rent out for a total of $1,400 - $1,600 per month, and he's only wanting 10% down. Even with the lower down payment and the 18 year amortization it still cash flows, and if I refinance after 5 years into a 30 yr mortgage, that's even more cash flow. 

Apologies if I'm leaving out any details, but ooking for opinions on this deal. Thanks in advance!