I would think on average a startup starts with more than one person.

What do they use as investment? Personal savings, loans, VC?

It depends upon the business. Startup costs are low here, and some businesses can be started and validated without registration or paperwork. Where formalization is a requirement, agents can register companies as cheaply as a couple of hundred USD, including a registered address. At the low end people use personal savings and family loans. At a slightly larger level friends tend to group together to reach capital requirements. Banks do loan but that's not as easy as it once was. There are government payouts available for specific sectors or achievements (eg. if patents are registered). At the higher end there is strong VC availability right now due to a combination of a relative crisis of faith (ie. no longer "it can never lose money!") in real estate, which was formerly the medium to long term investment traditionally considered most accessibly performant, and increased controls on cross-border capital flight.