Biggest reason for losing money?

[Nathan Gesner]

I know: turnover is the biggest expense. But let's be more specific. Is it:

1. Time sitting vacant during turnovers?

2. Losses due to excessive wear-and-tear?

3. Maintenance or capex?

4. Expensive property management?

5. Mistakes you've made as a Landlord?

6. Tenants constantly breaking their lease early?

What are the big-ticket expenses that are eating your lunch and stagnating your growth?