Answer: Before now. Before you start. Before you pick the business name. Before you lock in to a product. Before you and your partners sell the first item. Before you get signs made. Before you get your first customer. In other words, BEFORE THE LEGAL CRISIS.
Before you start. You want the IP lawyer to let you know if you can even legally start. Do you infringe patent(s)? How many? Can you modify to avoid infringing? Do you infringe a trademark or servicemark? How do you clear a business name? What business name? What business entity will you use? Are you willing to lose your house, boat, timeshare, motorcycle, bank account and car over this business - you might if you don't address this issue before you start. Sometimes once the deed is done, it cannot be undone. You cannot uninfringe once you infringe, that would be like unrobbing a bank or unmurdering a murder victim.
Before you pick the business name. Imagine buying thousands of dollars of signage, business stationery, business cars, gift pens, phonebook or Internet ads, etc. and then having to change the name and destroy all that stuff and also pay damages and attorney fees to someone for infringing their brand name. That can kill a startup business.
Before you lock in to a product. Imagine selling a product and getting thousands or orders and then getting a letter from the law firm McKool, Smith demanding $600 million dollars in damages for patent infringement. Research in Motion (Blackberry phones) did and that is what they paid to get out of it. And, where is Blackberry now after dominating the business smartphone market (remember back when Barack Obama "swore by his Blackberry"), yes where they are is trying to get out of the smartphone cellar after getting completely crushed by iPhone and Android. Patent infringement awards have reached the stratosphere, with Apple getting a 1.8 BILLION dollar patent infringement judgment against Samsung for copying the icon setup on the iPhone. And that is just the damages (which are just a cost of business to the giant Samsung). Injunctions, lawsuits, lawyer visits, legal fees, court costs, witness fees, discovery expenses, etc. all can kill a startup. So you need to get clearances on this stuff. You also want to be able to get your own patents so when that giant company tries to stomp you, you have something with which to fight back.
Before you and your partners sell your first product. Which product liability do you want to face? One where you got legal help beforehand, set up the right disclaimer and warnings and did the right legal work to insulate you and your assets from damages, or that surprise lawsuit from the guys on TV that promise to get your injured customer all the money they so rightfully deserve from your nefarious money grubbing uncaring filthy rich company that needs to give their client JUSTICE?
5.Before you get signs made. See 2. Signs bring business. Changing them embarasses your business and gives you a bad name and that scares business away.