That all depends on the state in which you are doing business. See a lawyer experienced in these matters for your state.
No attorney-client relationship exists. IRS Circular 230 Notice: No advice in this communication, including any attachment hereto is intended or written to be used, nor can it be used, for the purpose of avoiding penalties that may be imposed under the Internal Revenue Code.
You are encouraged to contact an attorney for assistance. If indeed a Texas LLC is the correct form of business, then you would be required to file the Certificate of Formation. However, you also need a Company Agreement and an EIN. Other documents will be required depending upon the nature of your business.
The above statements are provided as general information and not intended as legal advice. Each matter has its own set of unique circumstances that cannot be adequately addressed without consultation. You are strongly advised to hire an attorney licensed to practice law in your state to represent you.
Depends on which state you intend to start the business (It doesn't have to be a Texas entity). You need a good strong partnership agreement before you go any farther. That is, assuming you and your partner are friends, and want to remain friends. Get a written contract between you two regarding how the business is to function, roles, profit and loss split, contributions, indemnities, etc.
I am an attorney licensed to practice in Texas, Louisiana and before the United States Patent and Trademark Office. Laws vary from jurisdiction to jurisdiction and the above may not be an accurate assessment of the laws for your area. The above should be taken as general guidance and not specific legal advice. For specific legal advice you should seek a licensed attorney in your jurisdiction practicing in the area specific to your issue. The above does not constitute or establish an attorney client relationship. If you wish to receive specific advice about your legal issue, then contact my office to schedule a personal consultation.