There are a few main options for finding a place to live in London, one of the most vibrant, historic, and expensive cities in the world. Many of these options also apply to finding a home anywhere in the UK.
The cheapest option is to sqaut, which is to take up residence in a disused building, and set up home there. Squatting is at best semi-legal, and often illegal, as if the owner of the property decides to have you evicted you will have to leave. If you don't leave, eventually baliffs and or police will come and remove you from the place you are squatting. You could then try squatting somewhere else, or attempt to get some money together and rent a place to live.
There are lots of options here. You can pay your rent in cash, directly to the landlord (or to another tenant who sublets you a room) but more usually the landlord will expect you pay rent reguarly direct to his/her bank account by direct debit or standing order. Rental costs range from £50 per week for a room (very cheap) to thousands per month for a very nice house. In exchange for the exhorbitant amount paid monthly from you to him, your landlord (or landlord's agent) is responsible for maintaining the property and its fittings in good order. So, if your heating breaks down, the taps leak or the roof caves in, it is your landlord's duty to fix the problem AT NO COST TO YOU.
Many of the cheaper rented places are in a somewhat delapidated state, so don't expect a power shower, non dripping tap or double glazed windows unless you are prepared for the higher rent that these luxuries command. However, make sure that your rented property is in a reasonable state, before you move in and sign a contract, and check that your rental agreement states that the landlord will agree to fix problems within a reasonable time. Most standard contracts contain words to this affect.
Subletting is sometimes cheaper and more flexible than renting directly from a landlord, and the sublet is rarely contracted. Because of this, your rights are less well protected, and the subletter could choose to terminate the arrangement at anytime. This may mean that at short notice you have to leave, which puts you back on the streets again without a place to call home. If you are very lucky, you will have carefully save enough money in the years renting a cheap and crappy room to have the deposit to buy a home of your own.
BUYING A HOUSE
You will need about £150,000 to buy a small flat on the outskirts of London, and a deposit of up to 10%. These figures are roughly correct as of April 2005, but house prices rise very quickly, so be prepared for a shock if you look in an estate agents window. Deposit arrangements vary, if you pay less deposit the interest rate on the loan is usually higher.
Homes in the centre of London can cost of millions of pounds, palatial homes with many bedrooms come onto the market occasionally through high end dealers like Sothebys, and £250,000 for a three bedroom in a fairly central location is considered a bargain. If you see a home you like the look of on the market you can purchase it through the estate agent who is selling the proprty. This will be an expensive process, arrangement fees, a survey, stamp duty, and all sorts of other expenses. Unless you are already very rich you will need...
A mortgage is a long term arrangement with a bank or building society where the bank will loan you a large amount of money to purchase the home of your choice and allow you to live there idefinatley, providing you pay them an even larger sum of money in regular installments over the next few decades. This loan is 'secured' with the value of the property in which you live, so untill the mortgage is paid off in full you must keep up with your regular payments otherwise the bank can reposess the home and make you leave it.
If you pay off the mortgage, you will have paid the original cost of the home, and the 'interest' of the loan (which the bank charges for lending money) and the home will belong to you. And then you can be thankful that the roof that's beginning to sag, the outdated heating system, and battered floors are all your very own.