When you are ready to sell your property, you will be subject to depreciation recapture on all the depreciation you were eligible to take (whether you took the deduction or not) and may have to pay tax on some or all of it.
Because you have not taken depreciation in the past, considering amending your prior year's returns and take the appropriate depreciation expense. Losses are not necessarily a concern on rentals (due to depreciation) and it is quite common in the early years of operation.
https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
Depending on when you put the property in service, you may want to consider filing Form 3115 - Application for Change in Accounting Method instead of amending the prior returns. This will allow you to take all the prior depreciation at once on your current year tax return.
See this IRS website for Form 3115 -
http://www.irs.gov/pub/irs-pdf/f3115.pdfSee this IRS website for Form 3115 instructions -
http://www.irs.gov/pub/irs-pdf/i3115.pdf
