There are many levels to answer this question on. You can definitely take a laptop as a business expense.
Generally it is easier to prove its a business expense if you take a portion as a personal expense unless you have another PC or laptop for personal use.
2nd, upon a potential audit the IRS would want to know why you used it for just one property. It would be easier to explain that the laptop is used to take photos of all the properties, manage e-mails with all tenants or keep the books and records of each unit. If you are taking a loss on one property and are trying to load up the expenses for that property that would be a flag, So I would allocate the laptop to all your rentals.
And last, given its such a small expense, the IRS would not be keying in on these types of items. They will be looking more at rental income versus mortgage costs and maintenance costs, etc... I hope this helps.
