If you're in the market for another Buy to Let flat or house, there are lots of reasons to steer well clear of unoccupied properties. It's especially true if they have been empty for a while or are in very bad shape. The time and expense of renovating a property will often take a good chunk out of your short term profits. That's why it pays to take a more long term view and consider the value you will add to the property.
But don't dismiss unoccupied properties out of hand entirely. Every cloud has a silver lining. And there are some benefits of taking on a property that has been unnoccupied for a while. One thing to remember is that renovations on places that have been unoccupied for two years or more can often attract a VAT reduction to 5%. If you're undertaking a large programme of repairs, that VAT reduction can mean making a significant saving on the total cost. Get the all clear from your accountant though, before you make any big decisions.
A property can be empty for all sorts of reasons and they might not necessarily be bad ones. But do ensure that the area an empty property is located in is still one where there is significant demand for rentals. You can prove that a house has been vacant for the requisite period by using utility bills or the electoral register.