Seller financing a duplex

[Korey Scott]

Hello and thanks for stopping by to help!

i have a couple questions and see what everyone thinks! i would also like to have everyone's opinion on how to proceed! 

Okay, here is the deal. i have a someone i am speaking with about a duplex she owns. She wants to still live in the upstairs unit which is 2 bedrooms. Down stairs is 3 bedrooms. The leases are sublets per room at $400 per room. What i was think is offering to do a seller finance deal for 5 years with a balloon payment. i was going to have her live upstairs for free for a year instead of giving her a down payment. She is asking $99,000

Location is Kalamazoo Michigan 

Rents as far as i know total $1600 for the downstairs 

insurance is around $80

Taxes are around $150

payments to her i would assume to be around $800 

Any advice on how i should approach this i appreciate! thank you so much!