What should I look for when purchasing a system?
Make sure your contractor is licensed and been in business for at least 5 yrs, because a lot of businesses fail in the first 5 years. Warranties should be given to you in writing, technicians need to be factory trained, the company needs workers' compensation insurance, to protect you from a lawsuit if someone is injured on your property. The company should be a member of the Better Business Bureau and have excellent reputation referrals from friends or co-workers that have used the company in the past.
Make sure your proposal is very detailed and easy to understand.