Thanks for your question.
All the various forms will protect you from personal liability if established correctly. However, they very greatly in purpose and tax effects.
Your best option is going to be an LLC in which you are both 50% owners and managers. The LLC form will allow you to have "pass through" taxation and has very low regulatory and tax compliance costs.
A limited liability partnership and Limited partnership both require general partners which means you have to set up a different entity to be the general partner and the compliance and regulatory costs go up.
An S Corp would be the type of form you use if you had many more investors and needed to be able to transfer shares in the company. That doesn't sound like the situation here.
An regular C corp would be what you would want to eventually switch over to eventually if you are earning more than $500K per year, as there are different tax advantages that you can take at that point which will be help reduce your tax liability. However, unless your revenue is over $500K, the tax advantages are not going to be big enough to cover the costs of compliance/accounting and the time it takes.
An LLC is the way to go. There are LLC forms that you can fill out and file with the Texas Secretary of State
at the following website:
The LLC will only have a franchise tax statement which needs to be filed each year and a tax return. Other than that, there is not much in the way of yearly paper work.
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