There is no guarantee that you will be able to sell your shares when you want to, or at all.
Investments in early stage companies are generally long term, and you should not invest money if you are likely to need that money in the near or medium term. The timing and nature of your return is typically uncertain.
Returns can be realised in 4 ways:
Exit – a company may be acquired by a third party and distribute the proceeds to shareholders.
Listing – a company may list on a stock exchange like the NZX, providing a market for shareholders to sell their shares.
Dividends - a company may choose to distribute profits to shareholders in the form of dividends.
Private share sale – selling shares privately is generally lawful, however some companies may not facilitate it.