Installment sale interest vs. cap gain

[Andrew Meringoff]

Situation:

Found a seller who wants to sell but doesn’t want to pay 300k gain all at once.

Pure vacation property/second home. Bought for 359k will sell for 659k in this example.

Assuming 150k down payment in 2024 

50k annual payments for a year for 4 years 

259k ballon payment 

I thought 50% of each payment would be cap gains but then I read unstated interest payments and I’m lost.

What portion of his annual installment payments will be interest?

Can someone explain to me so I can explain to him how the deal would align with his stated goal of not paying 300k gains all at once? I thought I understood until I read section 483 and section 1274 and now I am lost.

Please help and thank you.