Thoughts on this seller finance deal?

[Robert Fowler]

My realtor turned me on to a property with seller financing.

The seller wants $465,000 and a 20% down payment. It sound like the terms are wildly flexible and I could potentially structure a deal where I cashflow $1200.00 a month after expenses. This would be amortized over 40 years at 5% interest and interested only payments with a 20 year balloon. I would be sacrificing the long term paydown of the loan for cashflow upfront. 

The returns seem good and this deal would leave me with just enough money to buy another home conventionally in the following 6-12 months if I can find the right houseback on the market. 

This is the first time I considered or been approached with this kind of deal, any input would be greatly appreciated!