Can I used 1099 income from one type of work to fund another startup business? Will I have to pay taxes on the 1099 income if it is reinvested in another business venture?

Any income you earn can be used for any legal activity.  The income reported to you on a 1099-MISC, (replaced by the new 1099-NEC), is taxable income.  There is no "rollover" rule in effect for 1099-MISC income that would allow you to defer the tax because you invested that money in another business venture.