Borrowing to raise cash to fund another property is known as gearing and the way you do this is through remortgaging.
Applying for a new mortgage on your existing property is much the same as applying for a loan to fund a house purchase.
You need to supply information about your income and outgoings and the rent on which the mortgage will be secured.
The lender will want to undertake a valuation although, in some cases, it will do this from outside the property.
On the legal side, the lender will want a conveyancer to undertake a local authority search and a search to prove you own the title to the property.
As there is no sale involved, there are no contracts to prepare, so the process should cost less than that surrounding a house purchase.
To attract customers, many lenders offer a remortgage package. This usually offers free legal work or a contribution towards legal fees, a free valuation and a reduced administration fee.
Where no remortgage package is available, you need to bear in mind that the costs associated will make a dent in your potential savings.