Some companies may require a 10% deposit, some may not require any. For larger projects, you'll almost always need to give a deposit, and it's good to ask how much the deposit will be before going forward with a project. The Berthoud contractor will know how much they need for a deposit when they've given you the estimate, so ask early.
Always ask for references, and always check them. Keep in mind though that the only references you'll get are people who the contractor is certain will give him a good review. You'd also be well advised to check online review sources in Berthoud as well, which will give you a broader view of customer satisfaction for a given company.