Cap gains question (seller financing)

[Peter Lee]

Say if you have a project that sells for $5 million but there is some form of seller financing where the buyer pays $2 million upfront and then the rest is paid over a 3 year period.  

Cost basis is say $1 million and for simplicity assume depreciation is zero.  So total profit is $4 million.

Is it true that the seller would only be liable for cap gains for the $2 million if say that was the only amount received for that tax year?

Any thoughts appreciated.