For writing off the taxes and insurance - which "he" are you asking about the seller or buyer ?

Seller would be receiving $250 to pay those taxes and insurance. Should be a wash.  I'd report on the Sched E or LLC or wherever he has been reporting this rental property in prior tax years.

Is the buyer keeping the rental property a rental property?  If yes, then yes paying $250/month for taxes and insurance is a deductible expense on Schedule E where all the other income and expenses would be reported.