Help understanding using equity to obtain more props

[Fred Shandler]

I know this is a very amateur question, but I don't understand how exactly equity is actually used in (or helps in) obtaining more properties.

For example, investors typically buy at 70% of market value, less repairs. Well, I thought banks only allow a 70% cash out refi? So in this case, wouldn't a cash out refi be irrelevant?

Isn't that what using one's equity is -cashing out through refinancing? Or do I have the wrong idea?

Clarification would be greatly appreciated!

-Fred