£25,000 gross income yes in some areas. Profit though is a different matter especially if you are mortgaged, use an agent (they'll take 20%+VAT) and have to outsource your cleaning, laundry, gardening and maintenance.
For those who have to pay for a changeover it averages £100 a time give or take depending where you are.
Add in cost of insurance, business rates, gardening, heating, lighting, wear and tear, damage and theft, mortgage repayments (commercial rates), boiler servicing, electrical inspections, annual redecoration, gardening. advertising etc etc and the profits can be very small.
There is also much more competition than there was now and the likes of Sykes and AirBnB are pushing prices down with many lets struggling to get the occupancy they once had. I'm happy with my returns but I have no mortgage and do not use an agent. I also do my own maintenance and repairs.