First Time Home Buyer Programs For Bad Credit How To Finance An Addition How to Get a Loan for a Garage Addition – Budgeting Money – Estimate Cost. Before you head to a bank or lender, determine the cost of adding a garage to your home. The initial figure will be an estimate at best. Obtain bids from contractors and go with the one you like best. The bid should clearly break down the cost of the garage in terms of materials and labor.