Thoughts on first buy and hold property using owner financing

[Josh Amidon]

I have an opportunity in Syracuse, NY to buy my first rental property using owner financing. 

The property is a duplex with one unit just rehabbed and currently vacant and the other unit currently renting for $800 but has not been raised in over 2 years. Both units are 4 bedrooms and 1 bath. 

The sales price is $55,000 with $10,000 down and then the rest spread over 20 years at 12%. Which might be steep but I just left my W2 job to start my own construction company full time. Taxes, insurance, water and electric are $4,000 a year total. 

My goal at this point is strictly cash flow. It seems like even with the high rate I have to pay it should cash flow well. Am i missing anything?