There is no definitive answer to how long it takes to receive a return. You may end up holding shares in a company for a long time, but that is not necessarily a bad thing. All products/markets mature differently and through wise investing you can predict what investments offer the fastest and highest ROI.
Usually you obtain ROI when the company is listed on a stock exchange, gets sold or pays a dividend. At some point there will be a secondary market for crowdfunding investments and you can sell your shares.