Seller finance deal peer review

[Thomas Corso]

Duplex is in SE Pennsylvania

Asking price - 200k 

Top /bottom duplex- 1 bedroom /2 bedroom

Total monthly profit- 1900

My offer- 206k offer price, 30 year loan with 5 year balloon, 10% down. 

Interest rate - variable 

Months 0-24 @ 4.5 %
months 25-60 @ 6% 

No penalty for prepayment before 5 year balloon.

Monthly loan will be roughly 1300 total PiTi

Cash flow -$600

Thoughts!? This is my first seller finance deal folks, so do not comment if you will bash. I just want to learn and grow and get constructive/helpful feedback.