I'm setting up a sole proprietorship in TX. What percentage of my net should I set aside to pay my taxes?

Answer 1

your social security (self employment tax) will be 15.3%
and then you Federal income tax added to all this, depends on your level of income,,

you'd send in a form 1040ES each quarter with tax estimate
don't just "set it aside" you'll end up paying a penalty for not having paid in enough tax.

Answer 2

That's about right, anywhere from 15.3% to 20% of your net, is about what your estimated tax payments should be!