You do not enter an expense called startup costs. You enter the type of expense for startup and then the date that the expense occurred.
You will want two separate business entries one for John and one for Elina. You enter the startup costs for each business under that business. Startup costs examples are: Market research, travel costs, salaries, consulting fees, accounting and legal fees.
If you had those expenses you enter each one in TurboTax. They have to have happened before the business was opened.
