do i need an LLC?

In which country are you based?
You can usually start as a sole entrepreneur (every country has some form of this entrepreneur scheme).  Then play it by ear as you grow your business.

About invoicing, it's tricky, it depends if you do online sales all over the world and also the US states. There are 2 things to consider.

1) One stop shop ( europe)
2) Nexus Law (USA)

other countries have similar laws, but I wouldn't worry too much about that (except for the UK)

If you'd like to be compliant without the headache, the best approach I found is to use an external system like Quaderno, that keeps tracks of territories and/or states for you. They will send you alerts when you need to pay taxes in a specific jurisdiction ( this is what happened to EA when she ran into problems with her european VAT ).

You can link quaderno with your software ( woo commerce), or directly to the Stripe or Paypal API if you process credit cards. once you have connected the payment gateway or processor to quaderno, Quaderno even creates the invoices for you! Magic! If you need a calendar, i would recommend that you start with Tidycal (it's a pay once use forever solution), to which you can connect stripe and paypal (you get my idea now about the invoicing and being up to norms).

Hello there! You don't nessecarly need an LLC, so you can also begin as a solepropriotiership, which does not need any act of formating an external legal entity. You can just start doing business. Basically, everyone is a solepropiortiership as soon as they do business outside of their employment status.

However, it is advisable and smart to form an LLC, since it protects you from all the liabilities, like debt, legal protection if someone suis your business and other things. As an example, if someone suis your business, or you have debt, which gets collected through debt enforcement law, they can only take down your LLC, so all of your private things under your name, and other LLCs/entities, cannot be touched by them, even if you had 10 million dollars in savings in cash in your bank under your name. So, basically, it gives you huge amounts of protection and tax benefits. It also gives you tax benefits, so you can save A LOT OF TAXES. On top of that, you feel much more professional, and you tend to be taken more seriously by others, but this is just a side note. If I would be you, I would form an LLC, because the investment is only 50-400 dollars, depending on which state you are in.

I don't know the rules in here yet, because I have just joined today, so if I am now allowed to share external links, I apolagize. If I am allowed to do that, I advise you to go to www.legalzoom.com. They offer a free service, where they create your LLC totally for free. The only thing you need to pay for is the mandatory state fee. I did it through this website, and it was absolutely easy. My LLC was setup within just 3-7 days. They will try to upsell throughout the process, but if you ignore them and click "no" all the time, the service will be 100% free of charge.

Hope this helps!