If I don't have receipts for second hand furniture I bought for a rental house, is it too risky to depreciate/expense it as the landlord? It was bought off craigslist.

If you are confident in your ability to show proof of purchase and the amount is reasonable for the condition of the furniture you should take the deduction.  

You will have a choice to deduct this as a miscellaneous expense under a special safe harbor election or depreciation.

It's best if you gather some kind of proof of purchase. If you have the ad from Craigslist, a picture of the furniture and even a confirmation of delivery to the tenants might be helpful.

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