Regarding startups.... This is what I have found:

The best work I have ever gotten has always been from referals. The best way to get referral is to get out there and be working. I would approach it the same way if I started now as I did back in 1996. I got myself a cheap van and minimum tools and got out there. Keep your prices low. As you get too much work to handle bump your prices. Cancel smaller noprofitable jobs for better ones only if you have to. Only time and experience will teach who is a waste of time and who is a good contact.

Buy tools as you need them. No reason to have brand new tools revolving on the charge account if you have no reason to plug in yet. All the time & money spent on advertising, shirts, etc., forget it. Those things are great as growth tools, but I wouldn't count on them to drum up much to start with. Instead, think of it this way:

Rather than charge $75/ hour, charge $50. Work 10 hours for $250 less. $500 more than you would have earned sitting at home waiting for the phone to ring with $250 being invested in a referal. And if your cheap, the referals are almost a guarenteed sell.
Now when you have 30-40 hrs a week consistantly booked 2-3 weeks out, keep looking at and estimating, but bump that price a little. Keeping your overhead low is the only way to make this work.

As time goes on all those contacts you've made over the years will really start to pay dividends. The contact base grows exponentially, but the only way to get it started and keep it going is to be out there and stay out there.