Do a cost estimate with a contractor, then have multiple contractors prepare bids. Most home renovation projects tend to go 15 to 20 percent over budget. Robyn says you need to set a budget and ask contractors for line by line descriptions of items for the renovation. She says you should also have a clear idea of your project. "You need to figure out in sort of a general way what you are doing," Robyn says. "Are you doing a bathroom? Are you doing the kitchen? Or are you adding a wing?"   

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