this is direct quote from IRC section 195
"The term “start-up expenditure” means any amount—
(A)paid or incurred in connection with—
(i)investigating the creation or acquisition of an active trade or business, or
(ii)creating an active trade or business, or
(iii)any activity engaged in for profit and for the production of income before the day on which the active trade or business begins, in anticipation of such activity becoming an active trade or business, "
therefore considering the amount, it would be deductible in the year you commenced the rental activities.
if in 2021 then you apparently have no deductible expenses and obviously no income so a return would not be required.
if this activity is not engaged in for profit you would have a hobby that would severely limit what you could deduct and even which forms to use.
