I ran a self proprietiorship window installation business... I felt I only needed the comp 4 a few templated things like a company stationery, a few marketing booklets 2 be made for ongoing clients 2 promte the business. The comp was (600-700 dollars and a software suite install was about 600 dollars) this included picture it publishing 4 marketing booklets 2 potential general contractors and also was good 4 biz cards, evelope printing with logo for return address, pre-printing marketing ads 4 sending out to a local mass mailer. I would also suggest also Quickbooks 4 accounting and you should be set.
700+600+250= $1550/comp.. if you plan 2 have a few comps installed through a gateway or router than times by the amount you need and add a little 4 the extra routering products and possibly extra 4 installation if not planning 2 do yourself.