Can seller rent back payment be treated as reduction of the house purchase price?

I purchased a house for my primary residence, which is closed in April, 2017. In the purchase contract, there is a seller rent back agreement to allow the seller rent it back for a month. And we did not move in to the house until a month later in May, 2017. The seller paid me some money as the rent for that month. From other posts (Like this: https://ttlc.intuit.com/questions/3383082?_ans=1&_pos=3&_src=sapi&_tot=259951&from=sapi&tags😃 it seems I have 2 options for the payment: 1. Treat it as reduction of the purchase price. 2. Report it as not for profit rental income. I prefer #1 so I don't have to pay tax on the payment, however I can find any IRS reference which states this is an option. Can anyone share the IRS reference which confirms #1 is an option?