Many people are now renting properties either through estate agents, private landlords or local housing groups / councils. Buying a house is harder than ever with many mortgage companies asking for at least a 10% deposit. This is simply out of reach for many people and therefore renting is often the only option. There can be advantages and disadvantages of renting a property and often the rules of what you can and cant do vary drastically between landlords.
If you are in a long term let the landlord may well be happy for you to do some decorating in the house as long as it is tasteful and nothing that cannot be changed easily if you were to move out.
If you have been in a property for a number of years then you may find that the landlord ill contributes towards some of the work. This is often only the case though if there is something wrong with the décor such as the carpets are all stained or the bathroom facilities are leaking etc. If you simply just want to change the décor because you fancy something different then you are not likely to get any financial help from the landlord.
Always ensure that you have permission from the landlord or estate agent prior to starting any work.