just looked at your site. van looks good, you got the system, insured, you look pro enough. A day only lasts as long as your water anyway.so 2 men half a day at a time or 1 man all day, makes no odds. If they ask, which they won't, you just tell them you prefer doing new jobs yourself, especially the first time. All they want is the job done. As already said, you will have to wait min 30days for your payment so maybe factor a bit of 'waiting time' in your quote and don't be afraid to ask for your money when its due.