Hello, theberkeleyep.
You can use the class tracking feature to track your two businesses. This is available in QuickBooks Online Plus, if you're not using a Plus version, upgrade your plan once you're ready.
However, combining two businesses in one account is not advisable, the transactions might be messed up. To avoid this, I recommend using a different account for the two.
You can also check this link to compare all the products offered by QuickBooks Online: https://quickbooks.intuit.com/.
Leave a comment below if you need further assistance. I'm always here to help.