She executed agreement on 09/12/22 and received $5,000 on 09/17/22.

She will not receive any additional until Jan 2023 when building is sold. Although...the way I read her agreement, she is entitled to receive $15,000 5 days after she vacates as long as she notices the landlord (otherwise 120 days) so she could receive more in 2022 assuming she vacates and properly notifies.

I'm not sure what the sales date is in this case. Can I get input on that? For an installment sale, wouldn't the sales date have to be in tax year 2022?