5 years of hard lessons and nearly 100 web sites as a freelancer. Here is what I have for you guys.
1) for all ecomm use open source scripts like zencart or oscommerce and make sure to look at the plugins
2) use other open source scirpts too like phpbb or gallery2 or phpnuke etc etc. There are tons of great scripts out there
3) outsource all your small jobs on scriptlance or gaf, jobs such as skinning these scripts with new graphics or at least headers to match
4) use banners to pay for your web hosting fees and little costs like domains and ssl certs
5) promote your system using affiliate marketing and ppc type programs
That is the quick and easy advice to should be on every web master's todo list!