have a look about and ask around for a garage to rent. these are often cheaper than lockups and will give you the space you need but not more (therefore saving cost) you'll need to get one with a water and electric supply obviously.
but as others have said, you'll need to work out all of the total cost of each (traveling, rent, water, electricity, time) of the 2nd premsis versus your home (water and electricity bill, but consider the convnience factor too)
and the final thing, charge your customers to accomadate the prices. if your running costs go up there is only one person whou should pay ... the customer, unfortunatley - that is business.