you really must talk to your mortgage lenders first. They may refuse permission, or insist that you gt a different mortgage. From eading round on the internet, some are happy to just let you do it, some insist that you change to a buy to ley mortgage. Whatever, it is illgal nt to tell them (althugh how would they know?)
you must:
Fit smoke alarms and extractor fans
Have gas appliances inspected by a CORGI-registered engineer
Ensure upholstered furniture is fireproof
Register with the Tenancy Deposit Scheme
Find out whether you need a House In Multiple Occupation licence.
Look at your buildings insurance - you will almost certainly need to change this.
While you are away who will sort out maintenance issues for you? if the boiler stops working, who will you get to go and fix it? who will pay for that?