How can I find out the amount of bedrooms a vacant property has?
you could try the County Auditors website
Check with your local assessor’s office either in person or online. These days, you can access the information online. The assessor’s property card will state the square footage, bedrooms, bathrooms, age etc. This should provide you with the information that you need.
You say that the property is vacant. If the windows aren’t boarded up, have you tried taking a peak. You can learn a lot from piecing the layout together from looking in the windows.