Always be careful in these types of situations. Do you remember signing a non-compete with your current company? If you see value ie. through a monetary sense

Always be careful in these types of situations. Do you remember signing a non-compete with your current company? If you see value ie. through a monetary sense OR another, I would speak to a employment Lawyer to make sure you can't get in trouble. Last thing you want is being sued for what your company lost in revenue + all other expenses. You must have some great talent id this other guy wants you as co-founder, keep up the good work.