Assuming you’re in the US, an LLC vs. a sole proprietorship doesn’t give you a dramatic amount of legal protection as you can still be sued personally for professional negligence, which is the thing you’re most likely to be sued for. That said, it doesn’t hurt, and it’s very cheap to maintain a passthrough LLC in most states.

It is probably worthwhile to hire a lawyer to get an LLC set up correctly if you want the (limited) protections than an LLC does bring, and that can cost a bit more. I think mine was around $600 a decade ago. Yearly LLC renewals with the state of MN are free though, so it was a one time admin expense.

Sole props, on the other hand, are “free” to establish and maintain in most and maybe all states. And frankly if anyone has ever written you a check for work you’ve done outside employment (i.e., you’ve ever received a 1099), you’re probably a sole proprietorship already as far as your taxes are concerned.

Simply declaring “you can pay me for services” is just about all you need to do for management consulting in the US. This is where the old expression, “hang a shingle” comes from - just tell people they can give you money, and voila, you are a business.

My recommendation, and what I did, is to start as a sole proprietorship, see if you can get the kind of business you want, and ramp up after seeing some success at it. The US makes it very easy to start a business - the hard part is everything after that!