FSBO advice needed for newbie

[David Scott Kelly]

I have an opportunity to get a hot Town home in Garland , Tx for 180K ...worth 200k . need a little work. rents 1500 -1600....always full ..seller firm at 180...might get him to 177.5...I will be  few hundred underwater if done conventionally. Seller said not too worry ..he will let me pay 10 per cent down and amortize at 30 years but with balloon payment at 5 yrs..

His accountant supposed to call with more #'s soon. Do I have more wigle room with seller holding the note ? 

Meaning...ok to lose a few hundred a month temporarily to get the deal ?

Thes townhomes were worth 60- 80K in 20005. 
 

And, I am newbie with very good  credit and have cash reserves. I work full time as an RN (20 yrs).