When buying a property, or re-mortgaging, rather than take your word for it, the lender will need a valuation of your intended property purchase, to ensure that what you’re asking to borrow, coincides with the property’s value. In fact, they’ll insist upon it.
It’s well worth investing in a survey too. This will tell you about the general condition of the property. If you’re investing in a property that’s older, or in a general state of disrepair, it would be well worth investing a little extra in a structural survey.