celtic, there are many already out there. they are called guesstimators.
automate the process. The longest part should be the take off. Automate your assemblies and go from there. You can either use a bid program or create your own excel sheet.
one point of reference, if you truly want to just be in the field, look to take on a partner. You will need someone to monitor the business side of everything, otherwise you will perpetually go through the peaks and valleys and never have any real momentum or continuity.
