There is no one time that is better than the next for starting your own firm. There is one key ingredient though. The key ingredient is a paying client with a project. So, as the cliche goes, don't give up your day job … until you have the key ingredient. To a lesser degree you also need to feel competent to do the work you are hired for. Let's cover that first.
You have to feel competent to work on your own or to have colleagues that can assist where you need help. However you can always hire the expertise you need to do the work. Nevertheless you should have a little experience in all facets of designing a project, getting bids, and administering construction. But you wouldn't even be thinking about the possibility of your own firm if you didn't have this issue covered.
If you can get the clients, you can always find a way to get the work done. The opposite is also true, but with a footnote. It is much easier to hire design help who will produce results than it is to hire business development help who will produce clients. As far as I can tell, this is because the more dependable the business development helper is at corralling work, the more likely he/she will be to start their own firm or find a better-paying opportunity elsewhere.
It is more likely, at least at first, that you will need to develop your business yourself. So how will you go about this. Well it helps if you have family connections, but you will find it easier to grow the firm more dependably if you develop a system for getting clients rather than only take advantage of work that is offered to you.
So what methods of business development should you consider?