If you are feeling the pinch financially after the Christmas holidays, there are a few things that you can do to raise extra funds but if you have the space, renting out a room is likely to make the most difference to the housekeeping budget, as it’s effectively cash in hand. This is because the Inland Revenue has revised the Rent a Room scheme so that you can now make £7500 a year tax free (£144 a week) from renting furnished spare rooms in your main home (i.e. you have to be living in it). The details are here: https://www.gov.uk/rent-room-in-your-home/the-rent-a-room-scheme.
In terms of preparing for your lodger, you might have a suitable room already that requires minimal expense to set up. This is ideal, but if not, start with a fresh coat of light coloured, neutral paint and some neutral, thermally lined curtains from a shop such as Dunelm. These £15.99 ones are in the sale in their shortest version http://www.dunelm.com/product/cream-toledo-thermal-pencil-pleat-curtains-1000014042 but floor-length ones always look classier (even if they do block the heat from radiators a bit).
Then you need to ensure there is sufficient good quality furniture, and here, if you can’t repurpose things from the rest of the house, or find things on Ebay or in charity shops that work, Argos is your friend, because their things can be good value for money and their customer service is so excellent it kicks IKEA into the long grass, along with their Express Delivery options. Today, the code FURN15 entered at checkout will get you a discount of 15% as well (Argos periodically runs discounts of this type, by the way). This £89.99 white, Shaker-style Aspley bed comes in different sizes and gets excellent reviews; http://www.argos.co.uk/product/4989622. There is an optional under-bed drawer for £39.99 if the bedroom is really tight for storage space. Then Argos sell good quality £189 foam mattresses, which are delivered rolled up for rapid and simply delivery – you just need to let them expand and air for 48 hours after delivery. The Dormeo Antigua hybrid single mattress is excellent and again gets rave reviews – we have one at home and were delighted with it. http://www.argos.co.uk/product/4291107 It also comes with a free pillow but we gave that away as it was a bit high. You don’t have to provide any bedding or towels if you don’t want to – that can be the responsibility of the lodger.
In addition, your lodger will need a wardrobe, so you might want to look at the new £87.99 Malibu one, which has small drawers as well as a hanging space http://www.argos.co.uk/product/5609712. Finally, a bedside table, lamp and chair will all be appreciated. If you don’t have anything that matches already, try the half price Osaka £29.99 bedside table with three drawers (extra storage) https://www.argos.co.uk/product/5488696, the reduced £4.49 ColourMatch lamp in cream http://www.argos.co.uk/product/9103056 and so your lodger can relax in the evening, this £79.99 Bentwood chair with matching footstool and integral magazine holder (extra storage again) http://www.argos.co.uk/product/5717336.
Once all these are in, your room will look very bland, but airy, and you can decide whether you want to style it more artistically with accent colours such as dark blue or wine red, or whether you prefer to leave it for your lodger to make their own mark. If your budget permits, you can also put in useful items such as a wall-mounted flat screen TV, bookcase, additional chair, coffee table, and so on, or a desk and chair if you are having students lodge with you. A large cork pinboard is also very useful in terms of discouraging Blu-tack on walls and subsequent redecoration. A row of hooks on the wall or on the back of the door is great for coats/bathrobes, and a steel towel airer on the radiator good for them to dry their towels and little bits of washing. This one is sufficiently classy http://www.argos.co.uk/product/4615604
So a budget of £500 would allow you to decorate and fit out the room in an appealing style that would look good in letting photographs and allow the lodger to enjoy the basics, leaving you to make up to £7000 from rent. (Outside expensive cities, you might only make half of this, so you might want to consider that and budget a bit less accordingly for redecorating your room, but a light, airy room means a fast let and few voids).