Consider the situation if you separated the two into two different Schedule Cs -- would you use the same office space for both? Would you use the same supplies? Would you use the same vehicle? Or would you use a home office for one Schedule C and only use your vehicle for one Schedule C -- therefore not intermingling your expenses for both Schedule Cs.
To me, it is less likely to cause a red flag if the two are combined when the same resources will be used for both "businesses". Otherwise, you will need to maintain meticulous records to separate your expenses for each Schedule C.
