That was a great site with some good info. What I m really looking for is info from someone who owns their own system who can tell me what the actual cost are going to be. Round about at least. I know that there will be a difference based on the brand of the compressor and other options as well. All of the sites that I have looked at say low maintenance costs but no one really tells what that low cost is. Allot of the mobile units look nice but I am not against having a compressor in the garage. Also something else that I would like to know about would be a storage system as well. When it comes time to filling the tanks it would not be unlikely to have to fill 6 - 9 tanks for a day of diving. I think that would take quite a long time off a mobile unit. I think that it was called a cascade system on one of the sites that I looked at.