Buying subject to then selling on land contract

[Jeff Fairchild]

Ok, so what are the pitfalls to buying a property subject to and then offering owner financing and reselling it right away for a higher price and higher interest rate? Ex.

I have one now w/ $127,000 mortgage, $759/mo 5.875%
I put $10,000 in repairs
then sell for $209,000 w/ $12,000 down from new buyer (to pay for repairs) at 7.75% for $1411 / mo

Would this deal work? What would I need to keep in mind? What happens if the seller demands that I get the mortgage out of his name in 3 years?