Apply for a pre-approved mortgage, which is usually good for 90 days. This will set your mortgage amount and interest rate, so you can set your budget before starting to house hunt. It also lets the home-seller know you are serious about buying when you decide to make an Offer to Purchase.
Don't forget to budget for extra expenses, such as moving, major appliances, utility hook-ups, home-ownership insurance and if this is your first home you may need to budget for some home maintenance equipment like lawn mower, garbage cans, gardening tools etc.
Prepare and budget for closing costs. Appraisal fees, title insurance, legal fees, survey, land transfer tax, prepaid property taxes or utilities are costs that can quickly add up and often come as a surprise for an unprepared first time home buyer.
Also, plan on including the cost of a home inspection in your budget. Avoiding any unexpected costs, like a new roof, is well worth the added expense.