I need help to start a wholesaling company
You can be your own registered agent but personally, I used a registered agent per my CPA's recommendation. Be careful about who you choose. Some of the online services are the same company masked as different companies and their fees, annual renewals and customer service are no good! Do your research to make sure they're a fit for you.
Yes, a registered agent is required to start a LLC. You could be your own but I'd definitely suggest using a third party. Be selective about who you choose since they will be responsible for receiving and forwarding important correspondence as it relates to the LLC in a timely manner.
You can also pay someone a small fee to act as your registered agent and establish the LLC yourself. But I generally recommend new investors to find an experienced attorney to help you set up your first LLC and explain how to operate it correctly. If you establish it wrong, or don't operate it correctly, then the LLC doesn't actually provide you the liability protection you expect. After the first LLC you can decide how you want to proceed - but for the first one it is strongly recommended.
This isn't legal advice, just my opinion as a real estate investor.